Chem Final

1.

What is the correct Lewis structure for hypochlorous acid, a compound containing chlorine, hydrogen and oxygen?.. .. : Cl : O : H : .. .. .. .. : Cl : H : O : .. .. .. .. : Cl : O : H .. .. .. .. O : Cl : H .. ..(Total 1 mark)

A.

B.

C.

D. 2.

When hydrogen peroxide decomposes, the temperature of the reaction mixture increases. 2H2O2(aq) O2(g) + 2H2O(l) What are the signs of H, S and G for this reaction? H A. B. C. D. + S + + + G +(Total 1 mark)

3.

Bromine and nitrogen(II) oxide react according to the following equation. Br2(g) + 2NO(g) 2NOBr(g) Which rate equation is consistent with the experimental data? [Br2] / mol dm 0.10 0.20 0.20 A. B. C. D. rate = k[Br2] [NO] rate = k[Br2] [NO] rate = k[Br2]2 2 2 3

[NO] / mol dm 0.10 0.10 0.40

3

Rate / mol dm s 1.0 10 4.0 10 4.0 106 6 6

3 1

rate = k[NO]

2

(Total 1 mark)

4.

Which step is the rate-determining step of a reaction?1

IB Questionbank Chemistry

A. B. C. D.

The step with the lowest activation energy The final step The step with the highest activation energy The first step(Total 1 mark)

5.

1 Consider the following graph of ln k against T (temperature in Kelvin) for the second order decomposition of N2O into N2 and O.N2O N2 + O

1 / 10 3 1 T K(a) State how the rate constant, k varies with temperature, T. ...................................................................................................................................... ......................................................................................................................................(1)

(b)

Determine the activation energy, Ea, for this reaction. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

......................................................................................................................................(3)

(c)

The rate expression for this reaction is rate = k [N2O] and the rate constant is 0.244 dm mol s at 750 C. A sample of N2O of concentration 0.200 mol dm is allowed to decompose. Calculate the rate when 10 % of the N2O has reacted. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2) (Total 6 marks)3 3 1 1

2

6.

The rate information below was obtained for the following reaction at a constant temperature. 2NO2(g) + F2(g) 2NO2F(g) [NO2] / mol dm 2.0 10 4.0 10 4.0 103 3 3 3

[F2] / mol dm 1.0 10 1.0 10 2.0 102 2 2

3

Rate / mol dm s1

3

4.0 10 8.0 10 1.6 10

4 4 3

What are the orders of the reaction with respect to NO2 and F2? A. B. C. D. 7. NO2 is first order and F2 is second order NO2 is second order and F2 is first order NO2 is first order and F2 is first order NO2 is second order and F2 is second order(Total 1 mark)

Consider the following reaction. 2NO(g) + 2H2(g) N2(g) + 2H2O(g) A proposed reaction mechanism is: NO(g) + NO(g) N2O2(g) N2O2(g) + H2(g) N2O(g) + H2O(g) N2O(g) + H2(g) N2(g) + H2O(g) What is the rate expression? A. B. rate = k[H2] [NO]2

fast slow fast

rate = k[N2O2] [H2]3


C. D. 8.

rate = k[NO] [H2]2

2

2

rate = k[NO] [N2O2] [H2](Total 1 mark)

2

Hydrogen and nitrogen(II) oxide react according to the following equation. 2H2(g) + 2NO(g) N2(g) + 2H2O(g)

At time = t seconds, the rate of the reaction is rate = k[H2(g)][NO(g)] (i)2

Explain precisely what the square brackets around nitrogen(II) oxide, [NO(g)], represent in this context. ...................................................................................................................................... ......................................................................................................................................(1)

(ii)

Deduce the units for the rate constant k. ...................................................................................................................................... ......................................................................................................................................(1) (Total 2 marks)

9.

Which experimental procedure could be used to determine the rate of reaction for the reaction between a solution of cobalt chloride, CoCl2(aq), and concentrated hydrochloric acid, HCl(aq)? Co(H2O)6 (aq) + 4Cl (aq) A. B. C. D.2+

CoCl4 (aq) + 6H2O(l)

2

Measure the change in pH in a given time Measure the change in mass in a given time Use a colorimeter to measure the change in colour in a given time Measure the change in volume of the solution in a given time(Total 1 mark)

10.

Sodium thiosulfate solution, Na2S2O3(aq), and hydrochloric acid, HCl(aq), react spontaneously to produce solid sulfur, S(s), according to the equation below. S2O3 (aq) + 2H (aq) S(s) + SO2(aq) + H2O(l) A student experimentally determined the rate expression to be: rate = k[S2O3 (aq)]2 2 2 +

Which graph is consistent with this information?

(Total 1 mark)

11.

Alex and Hannah were asked to investigate the kinetics involved in the iodination of propanone. They were given the following equation by their teacher.H ( aq) CH3COCH3(aq) + I2(aq) CH2ICOCH3(aq) + HI(aq)+

Alexs hypothesis was that the rate will be affected by changing the concentrations of the propanone and the iodine, as the reaction can happen without a catalyst. Hannahs hypothesis was that as the catalyst is involved in the reaction, the concentrations of the propanone, iodine and the hydrogen ions will all affect the rate. They carried out several experiments varying the concentration of one of the reactants or the catalyst while keeping other concentrations and conditions the same, and obtained the results below. Composition by volume of mixture / cm Experiment 1.00 mol dm CH3COCH3(aq) 10.0 10.0 5.0 10.03 3 3

Water 60.0 50.0 65.0 65.0

1.00 mol dm + H (aq) 10.0 10.0 10.0 5.0

3

5.00 10 3 mol dm I2 in KI 20.0 30.0 20.0 20.0

Initial rate 3 / mol dm s1 6 6 6 6

1 2 3 4 (a)

4.96 10 5.04 10 2.47 10 2.51 10

Explain why they added water to the mixtures. ...................................................................................................................................... ......................................................................................................................................(1)


5

(b)

(i) Deduce the order of reaction for each substance and the rate expression from the results. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(ii)

Comment on whether Alexs or Hannahs hypothesis is correct. ........................................................................................................................... ...........................................................................................................................(1)

(c)

Using the data from Experiment 1, determine the concentration of the substances used and the rate constant for the reaction including its units. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(3)

(d)

(i) This reaction uses a catalyst. Sketch and annotate the Maxwell-Boltzmann energy distribution curve for a reaction with and without a catalyst on labelled axes below.

(3)

(ii)

Describe how a catalyst works. ........................................................................................................................... ...........................................................................................................................(1) (Total 11 marks)

12.

The following data were obtained for the reaction between gases A and B. Experiment Initial [A] / mol dm3

Initial [B] / mol dm

3

Initial rate / mol dm min

3

1

1 2 3

1.0 10 2.0 10 2.0 10

3 3 3

1.0 10 1.0 10 2.0 10

3 3 3

2.0 10 2.0 10 4.0 10

4 4 4

Which relationship represents the rate expression for the reaction? A. B. C. D. 13. rate = k[B]2 2

rate = k[A] rate = k[A] rate = k[B]

(Total 1 mark)

Consider the following reaction. NO2(g) + CO(g) NO(g) + CO2(g) At T < 227 C the rate expression is rate = k[NO2] . Which of the following mechanisms is consistent with this rate expression? A. NO2 + NO2 N2O4 N2O4 + 2CO 2NO + 2CO2 NO2 + CO NO + CO2 NO2 NO + O CO + O CO2 NO2 + NO2 NO3 + NO NO3 + CO NO2 + CO2 fast slow slow slow fast slow fast(Total 1 mark)2

B. C.

D.

14.

Consider the following reaction. 2P + Q R + S This reaction occurs according to the following mechanism. P+QX P+XR+S What is the rate expression? A. B. C. D. rate = k[P] rate = k[P][X] rate = k[P][Q] rate = k[P] [Q](Total 1 mark)2

slow fast

15.

What happens when the temperature of a reaction increases? A. The activation energy increases.7


B. C. D. 16.

The rate constant increases. The enthalpy change increases. The order of the reaction increases.(Total 1 mark)

(a) There are four structural isomers with the molecular formula C4H9Br. One of these structural isomers exists as two optical isomers. Draw diagrams to represent the three-dimensional structures of the two optical isomers.(2)

(b)

All the isomers can by hydrolysed with aqueous sodium hydroxide solution. When the reaction of one of these isomers, X, was investigated the following kinetic data were obtained. Initial [X] / 3 mol dm 2.0 10 2.0 10 4.0 102 2 2

Experiment 1 2 3 (i) (ii)

Initial [OH ] / 3 mol dm 2.0 10 4.0 10 4.0 102 2 2

Initial rate of reaction / 3 1 mol dm min 4.0 10 4.0 10 8.0 103 3 3

Deduce the rate expression for the reaction.(3)

Determine the value of the rate constant for the reaction and state its units.(2)

(iii) State the name of isomer X and explain your choice.(2)

(iv) State equations for the steps that take place in the mechanism of this reaction and state which of the steps is slow and which is fast.(2) (Total 11 marks)

17.

This question refers to the following reaction. X2 + 2Y 2XY The reaction occurs in a series of steps. X2 2X X + Y XY slow fast

What is the rate-determining step for this reaction mechanism? A. X2 + 2Y 2XY

B. C. D. 18.

X2 + Y XY + X X2 2X X + Y XY(Total 1 mark)

This question refers to the following reaction. X2 + 2Y 2XY The reaction occurs in a series of steps. X2 2X X + Y XY What is the rate expression for this reaction? A. B. C. D. rate = k[XY] rate = k[X2][Y] rate = k[X2] rate = k[2X](Total 1 mark)2

slow fast

19.

Consider the following reaction. 5Br (aq) + BrO3 (aq) + 6H (aq) 3Br2(aq) + 3H2O(l) The rate expression for the reaction is found to be: rate = k[Br ] [BrO3 ][H ] Which statement is correct? A. B. The overall order is 12. Doubling the concentration of all of the reactants at the same time would increase the rate of the reaction by a factor of 16. The units of the rate constant, k, are mol dm s . A change in concentration of Br or BrO3 does not affect the rate of the reaction.(Total 1 mark) 3 1 + 2 +

C. D. 20.

The rate expression for a reaction is: rate = k [X][Y] Which statement is correct? A. B. C. As the temperature increases the rate constant decreases. The rate constant increases with increased temperature but eventually reaches a constant value. As the temperature increases the rate constant increases.9


D. 21.

The rate constant is not affected by a change in temperature.(Total 1 mark)

Consider the following reaction mechanism. Step 1 Step 2 H2O2 + I H2O + IO

slow

H2O2 + IO H2O + O2 + I

fast

Which statement correctly identifies the rate-determining step and the explanation? A. B. C. D. 22. Step 2 because it is the faster step Step 1 because it is the slower step Step 1 because it is the first step Step 2 because it is the last step(Total 1 mark)

Nitrogen monoxide reacts at 1280 C with hydrogen to form nitrogen and water. All reactants and products are in the gaseous phase. (i) The kinetics of the reaction were studied at this temperature. The table shows the initial rate of reaction for different concentrations of each reactant. [NO(g)]/ 3 3 mol dm 10 5.00 10.00 10.00 [H2(g)]/ mol dm 10 2.00 2.00 4.003 3

experiment 1 2 3

Initial rate/ 3 1 mol dm s 105

1.25 5.00 10.00

Deduce the order of the reaction with respect to NO and H2, and explain your reasoning.(4)

(ii)

Deduce the rate expression for the reaction.(1)

(iii) Determine the value of the rate constant for the reaction from Experiment 3 and state its units.(2) (Total 7 marks)

23.

The gas-phase decomposition of dinitrogen monoxide is considered to occur in two steps.k1 N2(g) + O(g) Step 1: N2O(g) k2 Step 2: N2O(g) + O(g) N2(g) + O2(g)

The experimental rate expression for this reaction is rate = k [N2O]. (i) (ii) Identify the rate-determining step.(1)

Identify the intermediate involved in the reaction.(1) (Total 2 marks)

24.

The conversion of CH3NC into CH3CN is an exothermic reaction which can be represented as follows. CH3NC transition state CH3CN

This reaction was carried out at different temperatures and a value of the rate constant, k, was obtained for each temperature. A graph of ln k against 1/T is shown below.

(i) (ii)

Define the term activation energy, Ea.(1)

Construct the enthalpy level diagram and label the activation energy, Ea, the enthalpy change, H, and the position of the transition state.(3)

(iii) (iv)

Describe qualitatively the relationship between the rate constant, k, and the temperature, T.(1)

Calculate the activation energy, Ea, for the reaction, using Table 1 of the Data Booklet.(4) (Total 9 marks)

25.

Two species, P and Q, react together according to the following equation. P+QR The accepted mechanism for this reaction is P+P P2 fast P2 + Q R + P What is the order with respect to P and Q? P A. B. C. D. 1 1 2 2 Q 1 2 1 2(Total 1 mark)

slow

26.

The activation energy of a reaction may be determined by studying the effect of a particular variable on11


the reaction rate. Which variable must be changed? A. B. C. D. 27. pH Concentration Surface area Temperature(Total 1 mark)

Consider the following reaction studied at 263 K. 2NO(g) + Cl2(g) 2NOCl(g)

It was found that the forward reaction is first order with respect to Cl2 and second order with respect to NO. The reverse reaction is second order with respect to NOCl. (i) (ii) State the rate expression for the forward reaction.(1)

Predict the effect on the rate of the forward reaction and on the rate constant if the concentration of NO is halved.(2)

(iii) 1.0 mol of Cl2 and 1.0 mol of NO are mixed in a closed container at constant temperature. Sketch a graph to show how the concentration of NO and NOCl change with time until after equilibrium has been reached. Identify the point on the graph where equilibrium is established.(4) (Total 7 marks)

28.

Consider the following reaction. NO2(g) + CO(g) NO(g) + CO2(g) Possible reaction mechanisms are: Above 775 K: Below 775 K: NO2 + CO NO + CO2 2NO2 NO + NO3 NO3 + CO NO2 + CO2 slow slow fast(Total 2 marks)

Based on the mechanisms, deduce the rate expressions above and below 775 K. 29. State two situations when the rate of a chemical reaction is equal to the rate constant.(Total 2 marks)

30.

1 Consider the following graph of ln k against T for the first order decomposition of N2O4 into NO2.Determine the activation energy in kJ mol for this reaction.1

(Total 2 marks)

31.

What is the order of reaction with respect to NO2(g) and F2(g) given the following rate data at a certain temperature? [NO2(g)] / mol dm 0.1 0.2 0.13

[F2(g)] / mol dm 0.2 0.2 0.4

3

Rate / mol dm min 0.1 0.4 0.2

3

1

Order with respect to NO2(g) A. B. C. D. 32. first first second second

Order with respect to F2(g) first second first second(Total 1 mark)

Nitrogen(II) oxide reacts with hydrogen according to the following equation: 2NO(g) + 2H2(g) N2(g) + 2H2O(g) The table shows how the rate of reaction varies as the concentrations of the reactants are changed. Experiment 1 2 Initial [NO] / 3 mol dm 0.100 0.100 Initial [H2] / mol dm 0.100 0.2003

Initial rate / 3 1 mol (N2) dm s 2.5310 5.05106 6


13

3 4 (a)

0.200 0.300

0.100 0.100

1.0110 2.2810

5 5

Determine the order of reaction with respect to H2 and with respect to NO. H2 ................................................................................................................................ NO ..............................................................................................................................(2)

(b)

Write the rate expression for the reaction. .....................................................................................................................................(1)

(c)

Calculate the value for the rate constant, and state its units using the data from experiment 1. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(d)

A suggested mechanism for this reaction is as follows. H2 + NO X X + NO Y + H2O Y + H2 N2 + H2O fast step slow step fast step

State and explain whether this mechanism agrees with the experimental rate expression in (b). ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

(e)

Explain why a single step mechanism is unlikely for a reaction of this kind. ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................

.....................................................................................................................................(2)

(f)

Deduce and explain how the initial rate of formation of H2O compares with that of N2. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 13 marks)

33.

Which reaction has the greatest increase in entropy? A. B. C. D. SO2(g) + 2H2S(g) 2H2O(l) + 3S(s) CaO(s) + CO2(g) CaCO3(s) CaC2(s) + 2H2O(l) Ca(OH)2(s) + C2H2(g) N2(g) + O2(g) 2NO(g)(Total 1 mark)

34.

Which statements describe the action of a catalyst? I. II. III. A. B. C. D. It does not alter the H for a reaction. It increases the Ea for the reaction. It alters the mechanism (pathway) of a reaction.

I and II only I and III only II and III only I, II and III(Total 1 mark)

35.

Consider the reaction between gaseous iodine and gaseous hydrogen. I2(g) + H2(g) 2HI(g) H = 9 kJO

Why do some collisions between iodine and hydrogen not result in the formation of the product? A. B. C. D. 36. The I2 and H2 molecules do not have sufficient energy. The system is in equilibrium. The temperature of the system is too high. The activation energy for this reaction is very low.(Total 1 mark)

Curve X on the graph below shows the volume of oxygen formed during the catalytic decomposition of a 3 1.0 mol dm solution of hydrogen peroxide.15


2H2O2(aq) O2(g) + 2H2O(l)

Which change would produce the curve Y? A. B. C. D. 37. Adding water Adding some 0.1 mol dm hydrogen peroxide solution Using a different catalyst Lowering the temperature(Total 1 mark)3 3 3

At 25 C, 200 cm of 1.0 mol dm nitric acid is added to 5.0 g of magnesium powder. If the experiment is repeated using the same mass of magnesium powder, which conditions will result in the same initial reaction rate? Volume of HNO3 / cm A. B. C. D. 200 200 100 1003

Concentration of 3 HNO3 / mol dm 2.0 1.0 2.0 1.0

Temperature / C 25 50 25 25(Total 1 mark)

38.

Factors that affect the rate of a chemical reaction include particle size, concentration of reactants and the temperature of the reaction. (i) Define the term rate of a chemical reaction. ...................................................................................................................................... ......................................................................................................................................(1)

(ii)

List the three characteristic properties of reactant particles which affect the rate of reaction as described by the collision theory. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

...................................................................................................................................... ......................................................................................................................................(3) (Total 4 marks)

39.

On the axes below sketch two Maxwell-Boltzmann energy distribution curves for the same sample of gas, one at a temperature T and another at a higher temperature T . Label both axes. Explain why raising the temperature increases the rate of a chemical reaction.

................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................(Total 5 marks)

40.

Sodium carbonate and hydrochloric acid react according to the equation below. Na2CO3(s) + 2HCl(aq) CO2(g) + 2NaCl(aq) + H2O(l) Which conditions will produce the fastest initial rate with 2.0 g of powdered sodium carbonate? A. B. C. D. 100 cm of 1.0 mol dm hydrochloric acid at 323 K 50 cm of 2.0 mol dm hydrochloric acid at 323 K 100 cm of 1.0 mol dm hydrochloric acid at 348 K 50 cm of 2.0 mol dm hydrochloric acid at 348 K(Total 1 mark)3 3 3 3 3 3 3 3

41.

Under which conditions will the reaction between 1.0 g calcium carbonate and excess hydrochloric acid be the fastest? Assume that all reactions are carried out at the same temperature. A. B. One large piece of calcium carbonate and 2 mol dm hydrochloric acid One large piece of calcium carbonate and 1 mol dm hydrochloric acid173 3


C. D. 42.

Powdered calcium carbonate and 2 mol dm hydrochloric acid Powdered calcium carbonate and 1 mol dm hydrochloric acid(Total 1 mark)3

3

Powdered manganese(IV) oxide, MnO2(s), increases the rate of the decomposition reaction of hydrogen peroxide, H2O2(aq). Which statements about MnO2 are correct? I. II. III. A. B. C. D. The rate is independent of the particle size of MnO2. MnO2 provides an alternative reaction pathway for the decomposition with a lower activation energy. All the MnO2 is present after the decomposition of the hydrogen peroxide is complete.


43.

Alex and Hannah were asked to investigate the kinetics involved in the iodination of propanone. They were given the following equation by their teacher.H ( aq ) CH3COCH3(aq) + I2(aq) CH2ICOCH3(aq) + HI(aq)+

Alexs hypothesis was that the rate will be affected by changing the concentrations of the propanone and the iodine, as the reaction can happen without a catalyst. Hannahs hypothesis was that as the catalyst is involved in the reaction, the concentrations of the propanone, iodine and the hydrogen ions will all affect the rate. They carried out several experiments varying the concentration of one of the reactants or the catalyst whilst keeping other concentrations and conditions the same. Their results are shown graphically below.

(a)

Discuss whether either Alexs or Hannahs hypothesis is correct. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(b)

Explain why the reaction rate will increase with increasing temperature. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(c)

(i) This reaction uses a catalyst. Sketch and annotate the Maxwell-Boltzmann energy distribution curve for a reaction with and without a catalyst on labelled axes below.

(3)

(ii)

Describe how a catalyst works. ........................................................................................................................... ...........................................................................................................................(1) (Total 8 marks)

44.

Which unit could be used for the rate of a chemical reaction? A. B. C. D. mol mol dm3 3 1

mol dm s dm3

(Total 1 mark)

45.

Which of the following can increase the rate of a chemical reaction? I. II. III. A. B. C. D. Increasing the temperature Adding a catalyst Increasing the concentration of reactants

I and II only I and III only II and III only I, II and III19


(Total 1 mark)

46.

The graph below shows how the volume of carbon dioxide formed varies with time when a hydrochloric acid solution is added to excess calcium carbonate in a flask.

(i) (ii)

Explain the shape of the curve.(3)

Copy the above graph on your answer sheet and sketch the curve you would obtain if double the volume of hydrochloric acid solution of half the concentration as in the example above is used instead, with all other variables kept constant from the original. Explain why the shape of the curve is different.(4)

(iii)

Outline one other way in which the rate of this reaction can be studied in a school laboratory. Sketch a graph to illustrate how the selected variable would change with time.(2)

(iv)

Define the term activation energy and state one reason why the reaction between calcium carbonate and hydrochloric acid takes place at a reasonably fast rate at room temperature.(2) (Total 11 marks)

47.

A piece of zinc was added to aqueous nitric acid and the volume of hydrogen gas produced was measured every minute. The results are plotted on the graph below.

Which graph would you expect if the same mass of powdered zinc was added to nitric acid with the same

concentration?

(Total 1 mark)

48.

Which changes increase the rate of the reaction below? C4H10(g) + Cl2(g) C4H9Cl(l) + HCl(g) I. II. III. A. B. C. D. Increase of pressure Increase of temperature Removal of HCl(g)


49.

The Haber process enables the large-scale production of ammonia needed to make fertilizers. The equation for the Haber process is given below. N2(g) + 3H2 2NH3(g)

The percentage of ammonia in the equilibrium mixture varies with temperature.


21

(i)

Use the graph to deduce whether the forward reaction is exothermic or endothermic and explain your choice.(2)

(ii)

State and explain the effect of increasing the pressure on the yield of ammonia.(2)

(iii) Explain the effect of increasing the temperature on the rate of reaction.(2) (Total 6 marks)

50.

What is the best definition of rate of reaction? A. B. C. D. The time it takes to use up all the reactants The rate at which all the reactants are used up The time it takes for one of the reactants to be used up The increase in concentration of a product per unit time(Total 1 mark)

51.

Which factors can affect reaction rate? I. II. III. A. B. C. D. The state of the reactants The frequency of the collisions between particles The average kinetic energy of the particles


52.

Equal masses of powdered calcium carbonate were added to separate solutions of hydrochloric acid. The calcium carbonate was in excess. The volume of carbon dioxide produced was measured at regular intervals. Which curves best represent the evolution of carbon dioxide against time for the acid solutions shown in the table below.

25 cm of 2 mol dm HCl A. B. C. D. 53. I I I II

3

3

50 cm of 1 mol dm HCl III IV II I

3

3

25 cm of 1 mol dm HCl IV III III III(Total 1 mark)

3

3

What is the function of iron in the Haber process? A. B. C. D. It shifts the position of equilibrium towards the products. It decreases the rate of the reaction. It provides an alternative reaction pathway with a lower activation energy. It reduces the enthalpy change of the reaction.(Total 1 mark)

54.

(a)

Define the term activation energy, Ea.

...................................................................................................................................... ......................................................................................................................................(1)

(b)

State two conditions necessary for a reaction to take place between two reactant particles. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(c)

Sketch an enthalpy level diagram to describe the effect of a catalyst on an exothermic reaction.


23

(3) (Total 6 marks)

55.

(i)

Define the term rate of reaction.(1)

(ii) (iii)

State an equation for the reaction of magnesium carbonate with dilute hydrochloric acid.(1)

The rate of this reaction in (ii), can be studied by measuring the volume of gas collected over a period of time. Sketch a graph which shows how the volume of gas collected changes with time.(1)

(iv)

The experiment is repeated using a sample of hydrochloric acid with double the volume, but half the concentration of the original acid. Draw a second line on the graph you sketched in part (iii) to show the results in this experiment. Explain why this line is different from the original line.(4) (Total 7 marks)

56.

Hydrochloric acid is reacted with large pieces of calcium carbonate, the reaction is then repeated using calcium carbonate powder. How does this change affect the activation energy and the collision frequency? Activation energy A. B. C. D. increases stays constant increases stays constant Collision frequency increases increases stays constant stays constant(Total 1 mark)

57.

Which statement is true about using sulfuric acid as a catalyst in the following reaction?H ( aq ) CH3COCH3(aq) + I2(aq) CH3COCH2I(aq) + HI(aq)+

I. II. III. A. B. C. D. 58.

The catalyst increases the rate of reaction. The catalyst lowers the activation energy for the reaction. The catalyst has been consumed at the end of the chemical reaction.


Graphing is an important method in the study of the rates of chemical reaction. Sketch a graph to show how the reactant concentration changes with time in a typical chemical reaction taking place in solution. Show how the rate of the reaction at a particular time can be determined.(Total 4 marks)

59.

(a) A solution of hydrogen peroxide, H2O2, is added to a solution of sodium iodide, NaI, acidified with hydrochloric acid, HCl. The yellow colour of the iodine, I2, can be used to determine the rate of reaction. H2O2(aq) + 2NaI(aq) + 2HCl(aq) 2NaCl(aq) + I2(aq) + 2H2O(l) The experiment is repeated with some changes to the reaction conditions. For each of the changes that follow, predict, stating a reason, its effect on the rate of reaction.


25

(i) (ii) (b)

The concentration of H2O2 is increased at constant temperature.(2)

The solution of NaI is prepared from a fine powder instead of large crystals.(2)

Explain why the rate of a reaction increases when the temperature of the system increases.(3) (Total 7 marks)

60.

Excess magnesium, was added to a beaker of aqueous hydrochloric acid. A graph of the mass of the beaker and contents was plotted against time (line 1).

M

a s s

1 2 T i m e

What change in the experiment could give line 2? A. B. C. D. 61. The same mass of magnesium in smaller pieces The same volume of a more concentrated solution of hydrochloric acid A lower temperature A more accurate instrument to measure the time(Total 1 mark)

Which quantities in the enthalpy level diagram are altered by the use of a catalyst?

E

n

t h

a l p

I

y

I I I I I T i m e

A. B. C. D. 62.


Which equation corresponds to the lattice enthalpy for silver iodide, AgI? A. AgI(s) Ag(s) + I(g)

B.

1 AgI(s) Ag(s) + 2 I2(g)

C. D. 63.

AgI(s) Ag (aq) + I (aq) AgI(s) Ag (g) + I (g)(Total 1 mark)+

+

Which ionic compound has the greatest lattice enthalpy? A. B. C. D. MgO CaO NaF KF(Total 1 mark)

64.

Which change will not increase the entropy of a system? A. B. C. D. Increasing the temperature Changing the state from liquid to gas Mixing different types of particles A reaction where four moles of gaseous reactants changes to two moles of gaseous products(Total 1 mark)O

65.

G calculations predict that a reaction is always spontaneous for which of the following combinations O O of H and S ? A. B. C. D. +H and +S +H and S H and SO O O O O

O

O O

H and +S

(Total 1 mark)

66.

Some words used in chemistry can have a specific meaning which is different to their meaning in everyday English. State what the term spontaneous means when used in a chemistry context. ................................................................................................................................................ ................................................................................................................................................(Total 1 mark)

67.

Propene can be hydrogenated in the presence of a nickel catalyst to form propane. Use the data below to answer the questions that follow. Compound hydrogen propane propene Formula H2(g) C3H8(g) C3H6(g) HO f

/ kJ mol 0

1

S / J K mol + 131 + 270 + 267

O

1

1

104 + 20.4


27

(i)

Outline why the value for the standard enthalpy change of formation of hydrogen is zero. ...................................................................................................................................... ......................................................................................................................................(1)

(ii)

Calculate the standard enthalpy change for the hydrogenation of propene. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(iii) Calculate the standard entropy change for the hydrogenation of propene. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(iv)

Determine the value of G for the hydrogenation of propene at 298 K. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

O

(v)

At 298 K the hydrogenation of propene is a spontaneous process. Determine the temperature above which propane will spontaneously decompose into propene and hydrogen. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2) (Total 9 marks)

68.

Which reaction has an enthalpy change equal to a standard enthalpy change of formation, Hf ? All reactions occur at 298 K and 1.01 10 Pa. A. B. C4H8(g) + H2O(g) C4H9OH(l) 4CO2(g) + 5H2O(g) C4H9OH(l) +13 2

O

5

O2(g)

C. D. 69.

4C(s) + 5H2(g) +

1 2

O2(g) C4H9OH(l)(Total 1 mark)

8C(s) + 10H2(g) + O2(g) 2C4H9OH(l)

Which process has an enthalpy change that represents the lattice enthalpy of sodium chloride? A. B. C. D. NaCl(s) Na (g) + Cl (g) NaCl(s) Na(s) ++1 2

+

Cl2(g)

NaCl(g) Na (g) + Cl (g) NaCl(s) Na(s) + Cl(g)(Total 1 mark)

70.

Which is the correct order of increasing magnitude of lattice enthalpy (lowest first)? A. B. C. D. NaCl < KCl < MgS < MgO MgO < MgS < KCl < NaCl KCl < NaCl < MgS < MgO MgO < NaCl < KCl < MgS(Total 1 mark)

71.

(a)

The production of ammonia is an important industrial process. N2(g) + 3H2(g) 2NH3(g)

(i)

Using the average bond enthalpy values in Table 10 of the Data Booklet, determine the standard enthalpy change for this reaction.(3)

(ii)

The standard entropy values, S, at 298 K for N2(g), H2(g) and NH3(g) are 193, 131 and 192 JK mol respectively. Calculate S for the reaction and with reference to the equation O above, explain the sign of S .(4)1 1 O

(iii) Calculate G for the reaction at 298 K.(1)

O

(iv) Describe and explain the effect of increasing temperature on the spontaneity of the reaction.(2)

(b)

The reaction used in the production of ammonia is an equilibrium reaction. Outline the characteristics of a system at equilibrium.(2)

(c) (d)

Deduce the equilibrium constant expression, Kc, for the production of ammonia.(1)

(i)3

0.20 mol of N2(g) and 0.20 mol of H2(g) were allowed to reach equilibrium in a3

1 dm closed container. At equilibrium the concentration of NH3(g) was 0.060 mol dm . Determine the equilibrium concentrations of N2(g) and H2(g) and calculate the value of Kc.(3)IB Questionbank Chemistry 29

(ii) (e) (f)

Predict and explain how increasing the temperature will affect the value of Kc.(2)

Describe how increasing the pressure affects the yield of ammonia.(2)

In practice, typical conditions used in the Haber process are a temperature of 500 C and a pressure of 200 atmospheres. Outline why these conditions are used rather than those that give the highest yield.(2)

(g)

A catalyst of iron is used in the Haber process. State and explain how the catalyst affects Kc and the position of equilibrium.(3) (Total 25 marks)

72.

Which reaction has the most negative change in entropy? A. B. C. D. 2SO2(g) + O2(g) 2SO3(g) NH4Cl(s) NH3(g) + HCl(g) PbCl2(s) Pb (aq) + 2Cl (aq) C(s) + O2(g) CO2(g)(Total 1 mark)O 2+

73.

What is the standard free energy change, G , in kJ, for the following reaction? C2H5OH(l) + 3O2(g) 2CO2(g) + 3H2O(g) Compound C2H5OH(l) CO2(g) H2O(g) O2(g) A. B. C. D. 1650 1300 448 +1300(Total 1 mark)

Gf / kJ mol 175 394 229 0

O

1

74.

Which combination of ionic radius and ionic charge would result in the highest lattice enthalpy for an ionic compound? Ionic radius A. B. C. D. small large small large Ionic charge high high low low

(Total 1 mark)

75.

Consider the equations below. CH4(g) + O2(g) HCHO(l) + H2O(l) =x HCHO(l) + =y1 2

H H H

O

O2(g) HCOOH(l)1 2

O

2HCOOH(l) + =z

O2(g) (COOH)2(s) + H2O(l)

O

What is the enthalpy change of the reaction below? 2CH4(g) + 3 2 O2(g) (COOH)2(s) + 3H2O(l) A. B. C. D. 76. x+y+z 2x + y + z 2x + 2y + z 2x + 2y + 2z(Total 1 mark)1

Given the enthalpy change for the reaction below: 2H2(g) + O2(g) 2H2O(l) which statement is correct? A. B. C. D. The standard enthalpy change of combustion of H2(g) is 286 kJ mol . The standard enthalpy change of combustion of H2(g) is +286 kJ mol . The standard enthalpy change of formation of H2O(l) is 572 kJ mol . The standard enthalpy change of formation of H2O(l) is +572 kJ mol .(Total 1 mark)1 1 1 1

H = 572 kJ

O

77.

Which is a correct definition of lattice enthalpy? A. B. C. D. It is the enthalpy change that occurs when an electron is removed from 1 mol of gaseous atoms. It is the enthalpy change that occurs when 1 mol of a compound is formed from its elements. It is the enthalpy change that occurs when 1 mol of solid crystal changes into a liquid. It is the enthalpy change that occurs when 1 mol of solid crystal is formed from its gaseous ions.(Total 1 mark)

78.

Which reaction has the largest increase in entropy? A. B. H2(g) + Cl2(g) 2HCl(g) Al(OH)3(s) + NaOH(aq) Al(OH)4 (aq) + Na (aq)31 +


C. D.

Na2CO3(s) + 2HCl(aq) 2NaCl(aq) + CO2(g) + H2O(l) BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq)(Total 1 mark)

79.

The lattice enthalpy of magnesium chloride can be calculated from the Born-Haber cycle shown below.

(i) (ii)

Identify the enthalpy changes labelled by I and V in the cycle.(2)

Use the ionization energies given in the cycle above and further data from the Data Booklet to calculate a value for the lattice enthalpy of magnesium chloride.(4)

(iii) The theoretically calculated value for the lattice enthalpy of magnesium chloride is +2326 kJ. Explain the difference between the theoretically calculated value and the experimental value.(2)

(iv)

The experimental lattice enthalpy of magnesium oxide is given in Table 13 of the Data Booklet. Explain why magnesium oxide has a higher lattice enthalpy than magnesium chloride.(2) (Total 10 marks)

80.

Which reaction has the greatest increase in entropy? A. B. C. C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g) H2(g) + Cl2(g) 2HCl(g) N2(g) + 3H2(g) 2NH3(g)

D. 81.

C2H4(g) + H2(g) C2H6(g)(Total 1 mark)

The reaction between but-1-ene and water vapour produces butan-1-ol. C4H8(g) + H2O(g) C4H9OH(l) The standard entropy values (S ) for but-1-ene, water vapour and butan-1-ol are 310, 189 and 228 J K 1 mol respectively. What is the standard entropy change for this reaction in 1 1 J K mol ? A. B. C. D. 271 +271 107 +107(Total 1 mark)O 1 O 1

82.

A reaction has a standard enthalpy change, H , of +10.00 kJ mol at 298 K. The O 1 1 standard entropy change, S , for the same reaction is +10.00 J K mol . What is the value O 1 of G for the reaction in kJ mol ? A. B. C. D. +9.75 +7.02 240 2970(Total 1 mark)

83.

Consider the following Born-Haber cycle:

The magnitudes for each of the enthalpy changes (a to e) are given in kJ mol but their signs (+ or ) have been omitted. (i) State the names for the enthalpy changes c and d.(2)IB Questionbank Chemistry 33

1

(ii) (iii)

Deduce which two of the enthalpy changes a to e have negative signs.(1)

Determine the value for the enthalpy of formation of potassium bromide.(2)

(iv) Explain why the quantitative value for the lattice enthalpy of calcium bromide is larger than the value for the lattice enthalpy of potassium bromide.(2) (Total 7 marks)

84.

What is the standard entropy change, S , for the following reaction? 2CO(g) + O2(g) 2CO2(g) CO(g) S /J K mol A. B. C. D. 189 173 +173 +189(Total 1 mark)O 1 1

O

O2(g) 205

CO2(g) 214

198

85.

Which step(s) is/are endothermic in the Born-Haber cycle for the formation of LiCl? A. B. C. D. Cl2(g) Cl(g) and Li(s) Li(g) Cl(g) + e Cl (g) and Li(g) Li (g) + e Li (g) + Cl (g) LiCl(s) Cl2(g) Cl(g) and Cl(g) + e Cl (g)(Total 1 mark) + +

86.

Consider the following reaction. 2CH3OH(g) + H2(g) C2H6(g) + 2H2O(g)

(a)

The standard enthalpy change of formation for CH3OH(g) at 298 K is 201 kJ mol and for H2O(g) is 242 kJ mol . Using information from Table 11 of the Data Booklet, determine the enthalpy change for this reaction. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)1

1

(b)

The standard entropy for CH3OH(g) at 298 K is 238 J K mol , for H2(g) is 131 J K mol and for H2O(g) is 189 J K mol . Using information from Table 11 of the Data Booklet, determine the entropy change for this reaction. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)1 1 1 1

1

1

(c)

Calculate the standard change in free energy, at 298 K, for the reaction and deduce whether the reaction is spontaneous or non-spontaneous. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(3) (Total 7 marks)

87.

In some countries, ethanol is mixed with gasoline (petrol) to produce a fuel for cars called gasohol. (i) (ii) Define the term average bond enthalpy.(2)

Use the information from Table 10 of the Data Booklet to determine the standard enthalpy change for the complete combustion of ethanol. CH3CH2OH(g) + 3O2(g) 2CO2(g) + 3H2O(g)(3)

(iii) The standard enthalpy change for the complete combustion of octane, C8H18, is 5471 kJ mol . Calculate the amount of energy produced in kJ when 1 g of ethanol and 1 g of octane is burned completely in air.(2) (Total 7 marks)1

88.

Which ionic compound has the most endothermic lattice enthalpy? A. B. C. D. NaCl KCl NaF KF(Total 1 mark)

89.

Which change leads to an increase in entropy?35


A. B. C. D. 90.

CO2(g) CO2(s) SF6(g) SF6(l) H2O(l) H2O(s) NaCl(s) NaCl(aq)(Total 1 mark)

The Born-Haber cycle for MgO under standard conditions is shown below.

The values are shown in the table below. Process A B C D E F (i) (ii) (iii) (iv) 602 enthalpy change / kJ mol +150 +248 +736 + (+1450) 142 + (+844)1

Identify the processes represented by A, B and D in the cycle.(3)

Define the enthalpy change, F.(2)

Determine the value of the enthalpy change, E.(2)

Define the enthalpy change C for the first value. Explain why the second value is significantly

larger than the first.(4)

(v)

The inter-ionic distance between the ions in NaF is very similar to that between the ions in MgO. Suggest with a reason, which compound has the higher lattice enthalpy value.(2) (Total 13 marks)

91.

(i)

The standard enthalpy change of three combustion reactions is given below in kJ. 2C2H6(g) + 7O2(g) 4CO2(g) + 6H2O(l) 3120 2H2(g) + O2(g) 2H2O(l) 572 C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(l) 1411O

H = H = H = O O

O

Based on the above information, calculate the standard change in enthalpy, H , for the following reaction. C2H6(g) C2H4(g) + H2(g)(4)

(ii)

Predict, stating a reason, whether the sign of S for the above reaction would be positive or negative.(2)

O

(iii) Discuss why the above reaction is non-spontaneous at low temperature but becomes spontaneous at high temperatures.(2)

(iv) Using bond enthalpy values, calculate H for the following reaction. C2H6(g) C2H4(g) + H2(g)(3)

O

(v)

Suggest with a reason, why the values obtained in parts (i) and (iv) are different.(1) (Total 12 marks)

92.

Which reaction has the most negative H value? A. B. C. D. LiF(s) Li (g) + F (g) Li (g) + F (g) LiF(s) NaCl(s) Na (g) + Cl (g) Na (g) + Cl (g) NaCl(s)(Total 1 mark)+ + + +

93.

Which equation represents the electron affinity of calcium? A. B. Ca(g) Ca (g) + e Ca(g) Ca (g) + e +


37

C. D. 94.

Ca(g) + e Ca (g) Ca (g) + e Ca(g)(Total 1 mark)+

Which reaction causes a decrease in the entropy of the system? A. B. C. D. CaCO3(s) CaO(s) + CO2(g) 2H2(g) + O2(g) 2H2O(l) 2C(s) + O2(g) 2CO(g) 2SO3(g) 2SO2(g) + O2(g)(Total 1 mark)

95.

What are the signs of H and S for a reaction that is non-spontaneous at low temperature but spontaneous at high temperature? H A. B. C. D. + + (i) (ii)

S + +

(Total 1 mark)

96.

Define the terms lattice enthalpy and electron affinity.(2)

Use the data in the following table and from the data booklet to construct the Born-Haber cycle for sodium chloride, NaCl, and determine the lattice enthalpy of NaCl(s).

1 Na(s) + 2 Cl2(g) NaCl(g)Na(s) Na(g) H = +108 kJ mol 1

H = 411 kJ mol

1

(4)

(iii) Describe the structure of sodium chloride.(2) (Total 8 marks)

97.

When 100 cm of 1.0 mol dm HCl is mixed with 100 cm of 1.0 mol dm NaOH, the temperature of 3 the resulting solution increases by 5.0 C. What will be the temperature change, in C, when 50 cm of these two solutions are mixed? A. B. C. D. 2.5 5.0 10 20(Total 1 mark)

3

3

3

3

98.

Which statement about bonding is correct?

A. B. C. D. 99.

Bond breaking is endothermic and requires energy. Bond breaking is endothermic and releases energy. Bond making is exothermic and requires energy. Bond making is endothermic and releases energy.(Total 1 mark)

Consider the following reactions.

1 Cu2O(s) + 2 O2(g) 2CuO(s)Cu2O(s) Cu(s) + CuO(s) What is the value of H , in kJ, for this reaction?O

H = 144 kJ H = +11 kJO

O

1 Cu(s) + 2 O2(g) CuO(s)A. B. C. D. 144 + 11 +144 11 144 11 +144 + 11(Total 1 mark)

100. Methanol is made in large quantities as it is used in the production of polymers and in fuels. The enthalpy of combustion of methanol can be determined theoretically or experimentally.

1 CH3OH(l) + 1 2 O2(g) CO2(g) + 2H2O(g)(a) Using the information from Table 10 of the Data Booklet, determine the theoretical enthalpy of combustion of methanol. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(3)

(b)

The enthalpy of combustion of methanol can also be determined experimentally in a school laboratory. A burner containing methanol was weighed and used to heat water in a test tube as illustrated below.


39

The following data were collected. Initial mass of burner and methanol / g Final mass of burner and methanol / g Mass of water in test tube / g Initial temperature of water / C Final temperature of water / C (i) Calculate the amount, in mol, of methanol burned. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

80.557 80.034 20.000 21.5 26.4

(ii)

Calculate the heat absorbed, in kJ, by the water. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)

(iii)

Determine the enthalpy change, in kJ mol , for the combustion of 1 mole of methanol. ...........................................................................................................................

1

........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(c)

The Data Booklet value for the enthalpy of combustion of methanol is 726 kJ mol . Suggest why this value differs from the values calculated in parts (a) and (b). (i) Part (a) ........................................................................................................................... ...........................................................................................................................(1)

1

(ii)

Part (b) ........................................................................................................................... ...........................................................................................................................(1) (Total 12 marks)

101. Consider the two reactions involving iron and oxygen. 2Fe(s) + O2(g) 2FeO(s) H = 544 kJO O

4Fe(s) + 3O2(g) 2Fe2O3(s) H = 1648 kJ What is the enthalpy change, in kJ, for the reaction below? 4FeO(s) + O2(g) 2Fe2O3(s) A. B. C. D. 1648 2(544) 544 (1648) 1648 544 1648 2(544)(Total 1 mark)

102. Which processes have a negative enthalpy change? I. II. III. A. B. C. D. 2CH3OH(l) + 3O2(g) 2CO2(g) + 4H2O(l) HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) H2O(g) H2O(l)



41

103. Consider the following reactions. N2(g) + O2(g) 2NO(g) H = +180 kJ 2NO2(g) 2NO(g) + O2(g) What is the H value, in kJ, for the following reaction? N2(g) + 2O2(g) 2NO2(g) A. B. C. D. 1 (+180) + 1 (+112) 1 (+180) + 1 (+112) 1 (+180) + 1 (+112) 1 (+180) + 1 (+112)(Total 1 mark)O O

H = +112 kJ

O

104. If white anhydrous copper(II) sulfate powder is left in the atmosphere it slowly absorbs water vapour giving the blue pentahydrated solid. CuSO4(s) + 5H2O(l) CuSO45H2O(s) (anhydrous) (pentahydrated) It is difficult to measure the enthalpy change for this reaction directly. However, it is possible to measure the heat changes directly when both anhydrous and pentahydrated copper(II) sulfate are separately dissolved in water, and then use an energy cycle to determine the required enthalpy change value, Hx, indirectly.

(a)

To determine H1 a student placed 50.0 g of water in a cup made of expanded polystyrene and used a data logger to measure the temperature. After two minutes she dissolved 3.99 g of anhydrous copper(II) sulfate in the water and continued to record the temperature while continuously stirring. She obtained the following results.

(i)

Calculate the amount, in mol, of anhydrous copper(II) sulfate dissolved in the 50.0 g of water. ........................................................................................................................... ...........................................................................................................................(1)

(ii)

Determine what the temperature rise would have been, in C, if no heat had been lost to the surroundings. ........................................................................................................................... ...........................................................................................................................(2)


43

(iii)

Calculate the heat change, in kJ, when 3.99 g of anhydrous copper(II) sulfate is dissolved in the water. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(iv) Determine the value of H1 in kJ mol . ........................................................................................................................... ...........................................................................................................................(1)

1

(b)

To determine H2, 6.24 g of pentahydrated copper(II) sulfate was dissolved in 47.75 g of water. It was observed that the temperature of the solution decreased by 1.10 C. (i) Calculate the amount, in mol, of water in 6.24 g of pentahydrated copper(II) sulfate. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(ii)

Determine the value of H2 in kJ mol . ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

1

(iii) Using the values obtained for H1 in (a) (iv) and H2 in (b) (ii), determine the value for Hx in kJ mol . ...........................................................................................................................(1)1

(c)

The magnitude (the value without the + or sign) found in a data book for Hx is 78.0 kJ mol . (i) Calculate the percentage error obtained in this experiment. (If you did not obtain an answer 1 for the experimental value of Hx then use the value 70.0 kJ mol , but this is not the true value.) ........................................................................................................................... ...........................................................................................................................(1)

1

(ii)

The student recorded in her qualitative data that the anhydrous copper(II) sulfate she used was pale blue rather than completely white. Suggest a reason why it might have had this pale blue colour and deduce how this would have affected the value she obtained for Hx.

........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2) (Total 14 marks)

105. Propane can be formed by the hydrogenation of propene. CH3CH=CH2(g) + H2(g) CH3CH2CH3(g) (i) State the conditions necessary for the hydrogenation reaction to occur. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(ii)

Enthalpy changes can be determined using average bond enthalpies. Define the term average bond enthalpy. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(iii) Determine a value for the hydrogenation of propene using information from Table 10 of the Data Booklet. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(iv) Explain why the enthalpy of hydrogenation of propene is an exothermic process. ...................................................................................................................................... ......................................................................................................................................(1) (Total 7 marks)

106. Which equation represents the bond enthalpy for the HBr bond in hydrogen bromide? A. HBr(g) H(g) + Br(g)45


B.

HBr(g) H(g) + Br(l)

C.

1 HBr(g) H(g) + 2 Br2(1) 1 HBr(g) H(g) + 2 Br2(g)(Total 1 mark)

D.

107. Which types of reaction are always exothermic? I. II. III. A. B. C. D. Neutralization Decomposition Combustion


108. A pure aluminium block with a mass of 10 g is heated so that its temperature increases from 20 C to 1 1 1 50 C . The specific heat capacity of aluminium is 8.99 10 J g K . Which expression gives the heat energy change in kJ? A. B. 10 8.99 10 303 10 8.99 10 3010 8.99 10 1 303 1000 10 8.99 10 1 30 1000(Total 1 mark)1 1

C.

D.

109. In an experiment to measure the enthalpy change of combustion of ethanol, a student heated a copper 3 calorimeter containing 100 cm of water with a spirit lamp and collected the following data. Initial temperature of water: Final temperature of water: Mass of ethanol burned: 1.78 g 3 Density of water: 1.00 g cm (i) (ii) (iii) 20.0 C 55.0 C

Use the data to calculate the heat evolved when the ethanol was combusted.(2)

Calculate the enthalpy change of combustion per mole of ethanol.(2)

Suggest two reasons why the result is not the same as the value in the Data Booklet.(2)

(Total 6 marks)

110. The standard enthalpy changes for the combustion of carbon and carbon monoxide are shown below. C(s) + O2(g) CO2(g) Hc = 394 kJmol 1 CO(g) + 2 O2(g) CO2(g)O 1

Hc = 283 kJ mol

O

1

What is the standard enthalpy change, in kJ, for the following reaction?

1 C(s) + 2 O2(g) CO(g)A. B. C. D. 677 111 +111 +677(Total 1 mark)

111. Which is correct about energy changes during bond breaking and bond formation? Bond breaking A. B. C. D. exothermic and H positive exothermic and H negative endothermic and H positive endothermic and H negative Bond formation endothermic and H negative endothermic and H positive exothermic and H negative exothermic and H positive(Total 1 mark)

112. Which processes are exothermic? I. II. III. A. B. C. D. Ice melting Neutralization Combustion


113. Which statement is correct given the enthalpy level diagram below?


47

A. B. C. D.

The reaction is endothermic and the products are more thermodynamically stable than the reactants. The reaction is exothermic and the products are more thermodynamically stable than the reactants. The reaction is endothermic and the reactants are more thermodynamically stable than the products. The reaction is exothermic and the reactants are more thermodynamically stable than the products.(Total 1 mark)

114. Identical pieces of magnesium are added to two beakers, A and B, containing hydrochloric acid. Both acids have the same initial temperature but their volumes and concentrations differ.

Which statement is correct? A. B. C. D. The maximum temperature in A will be higher than in B. The maximum temperature in A and B will be equal. It is not possible to predict whether A or B will have the higher maximum temperature. The temperature in A and B will increase at the same rate.(Total 1 mark)

115. Which equation best represents the bond enthalpy of HCl? A. B. HCl(g) H (g) + Cl (g) HCl(g) H(g) + Cl(g)+

C. D.

HCl(g)

1 2

H2(g) +

1 2

Cl2(g)(Total 1 mark)

2HCl(g) H2(g) + Cl2(g)

116. The data below are from an experiment to measure the enthalpy change for the reaction of aqueous copper(II) sulfate, CuSO4(aq) and zinc, Zn(s). Cu (aq) + Zn(s) Cu(s) + Zn (aq) 50.0 cm of 1.00 mol dm copper(II) sulfate solution was placed in a polystyrene cup and zinc powder was added after 100 seconds. The temperature-time data was taken from a data-logging software program. The table shows the initial 23 readings.3 3 2+ 2+

A straight line has been drawn through some of the data points. The equation for this line is given by the data logging software as T = 0.050t + 78.0 where T is the Temperature at time t. (a) The heat produced by the reaction can be calculated from the temperature change, T, using the expression below. Heat change = Volume of CuSO4(aq) Specific heat capacity of H2O T Describe two assumptions made in using this expression to calculate heat changes. ......................................................................................................................................IB Questionbank Chemistry 49

...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(b)

(i) Use the data presented by the data logging software to deduce the temperature change, T, which would have occurred if the reaction had taken place instantaneously with no heat loss. ........................................................................................................................... ...........................................................................................................................(2)

(ii)

State the assumption made in part (b)(i). ........................................................................................................................... ...........................................................................................................................(1)

(iii)

Calculate the heat, in kJ, produced during the reaction using the expression given in part (a). ........................................................................................................................... ...........................................................................................................................(1)

(c)

The colour of the solution changed from blue to colourless. Deduce the amount, in moles, of zinc which reacted in the polystyrene cup. ...................................................................................................................................... ......................................................................................................................................(1)

(d)

Calculate the enthalpy change, in kJ mol , for this reaction. ...................................................................................................................................... ......................................................................................................................................(1) (Total 8 marks)

1

117. An experiment was designed to investigate how the enthalpy change for a displacement reaction relates to the reactivities of the metals involved. The following metals in order of decreasing reactivity were available.

Excess amounts of each metal were added to 1.00 mol dm copper(II) sulfate solution. The temperature change was measured and the enthalpy change calculated. (i) Suggest a possible hypothesis for the relationship between the enthalpy change of the reaction and the reactivity of the metal. ...................................................................................................................................... ......................................................................................................................................(1)

3

(ii)

Sketch a graph on the diagram below to illustrate your hypothesis.

(1) (Total 2 marks)

118. Hydrazine is a valuable rocket fuel. The equation for the reaction between hydrazine and oxygen is given below. N2H4(g) + O2(g) N2(g) + 2H2O(g) Use the bond enthalpy values from Table 10 of the Data Booklet to determine the enthalpy change for this reaction.(Total 3 marks)

119. When some solid barium hydroxide and solid ammonium thiosulfate were reacted together, the temperature of the surroundings was observed to decrease from 15 C to 4 C. What can be deduced from this observation? A. B. C. D. The reaction is exothermic and H is negative. The reaction is exothermic and H is positive. The reaction is endothermic and H is negative. The reaction is endothermic and H is positive.(Total 1 mark)

120. Which process represents the CCl bond enthalpy in tetrachloromethane? A. B. CCl4(g) C(g) + 4Cl(g) CCl4(g) CCl3(g) + Cl(g)51


C. D.

CCl4(l) C(g) + 4Cl(g) CCl4(l) C(s) + 2Cl2(g)(Total 1 mark)

121. Some water is heated using the heat produced by the combustion of magnesium metal. Which values are needed to calculate the enthalpy change of reaction? I. II. III. A. B. C. D. The mass of magnesium The mass of the water The change in temperature of the water


122. Two students were asked to use information from the Data Booklet to calculate a value for the enthalpy of hydrogenation of ethene to form ethane. C2H4(g) + H2(g) C2H6(g) John used the average bond enthalpies from Table 10. Marit used the values of enthalpies of combustion from Table 12. (a) Calculate the value for the enthalpy of hydrogenation of ethene obtained using the average bond enthalpies given in Table 10. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(b)

Marit arranged the values she found in Table 12 into an energy cycle.

Calculate the value for the enthalpy of hydrogenation of ethene from the energy cycle. ......................................................................................................................................

...................................................................................................................................... ......................................................................................................................................(1)

(c)

Suggest one reason why Johns answer is slightly less accurate than Marits answer. ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(1)

(d)

John then decided to determine the enthalpy of hydrogenation of cyclohexene to produce cyclohexane. C6H10(l) + H2(g) C6H12(l) (i) Use the average bond enthalpies to deduce a value for the enthalpy of hydrogenation of cyclohexene. ........................................................................................................................... ...........................................................................................................................(1)

(ii)

The percentage difference between these two methods (average bond enthalpies and enthalpies of combustion) is greater for cyclohexene than it was for ethene. Johns hypothesis was that it would be the same. Determine why the use of average bond enthalpies is less accurate for the cyclohexene equation shown above, than it was for ethene. Deduce what extra information is needed to provide a more accurate answer. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2) (Total 7 marks)

123. 1.0 g of sodium hydroxide, NaOH, was added to 99.0 g of water. The temperature of the solution increased from 18.0 C to 20.5 C. The specific heat capacity of the solution is 1 1 4.18 J g K . 1 Which expression gives the heat evolved in kJ mol ?

A.

2.5 100.0 4.18 1000 40.0 2.5 100.0 4.18 1000 40.0 2.5 100.0 4.18 40.0 1000

B.

C.


53

D.

2.5 1.0 4.18 40.0 1000(Total 1 mark)

124. Two students were asked to use information from the Data Booklet to calculate a value for the enthalpy of hydrogenation of ethene to form ethane. C2H4(g) + H2(g) C2H6(g) John used the average bond enthalpies from Table 10. Marit used the values of enthalpies of combustion from Table 12.

(a)

Calculate the value for the enthalpy of hydrogenation of ethene obtained using the average bond enthalpies given in Table 10. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(b)

Determine the value for the enthalpy of hydrogenation of ethene using the values for the enthalpies of combustion of ethene, hydrogen and ethane given in Table 12. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(c)

Suggest one reason why Johns answer is slightly less accurate than Marits answer and calculate the percentage difference. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(d)

John then decided to determine the enthalpy of hydrogenation of cyclohexene to produce cyclohexane. C6H10(l) + H2(g) C6H12(l) (i) Use the average bond enthalpies to deduce a value for the enthalpy of hydrogenation of cyclohexene. ...........................................................................................................................

...........................................................................................................................(1)

(ii)

The percentage difference between these two methods (average bond enthalpies and enthalpies of combustion) is greater for cyclohexene than it was for ethene. Johns hypothesis was that it would be the same. Determine why the use of average bond enthalpies is less accurate for the cyclohexene equation shown above, than it was for ethene. Deduce what extra information is needed to provide a more accurate answer. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2) (Total 9 marks)

125. What is the energy, in kJ, released when 1.00 mol of carbon monoxide is burned according to the following eq

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