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Higher (National 6) Unit 3: Chemistry in Society 3a Getting the most from reactants

Industrial Chemistry

1. Sulfur dioxide for the manufacture of sulfuric acid can be produced by burning sulfur or by roasting iron pyrites (FeS) in air.

a) At present most sulfur dioxide is made from sulfur, even though iron pyrites is cheaper. Use the flow diagram to suggest one good reason for using sulfur and one good reason for not using iron pyrites.

b) Air is a raw material. What feedstock does it supply in the above reactions and why is it chosen?

c) Suggest two changes in World market prices which chould lead to iron pyrites being the preferred feedstock for sulfur dioxide production.

2. The diagram below shows how sulfur dioxide is removed from the gases given off in a coal fired power station.

The gases released are passed through powdered limestone (calcium carbonate) in water.

a) Why would sulfur dioxide be removed from the waste gases?

b) Limestone is insoluble in water. A soluble carbonate would be more efficient. Suggest why limestone is used.

c) A by-product of the reaction makes the process more economically feasible. Name the by-product.

d) A power station produces 600 tonnes of sulfur dioxide per day. Calculate the mass of calcium carbonate required to remove this completely.

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3. The flow diagram shows how vinyl chloride (CH2=CHCl), an important feedstock, is made in industry.

a) What is a feedstock? b) What is the systematic name for vinyl chloride.c) Give a use for vinyl chloride.d)

i) Write the formulae for three substances which are recycled in the process shown.ii) Give a reason for recycling chemicals.

e) i) Write the equation for the reaction taking place in the cracker.ii) The reaction in the cracker is exothermic. Why is this an advantage?

f) Name the process taking place in the separator units.g) Name the type of reaction taking place in the scrubber unit.

4. Acetone, widely used as a solvent, is manufactured from cumene. Cumene is formed when propene reacts with benzene. Cumene is oxidised by air and the cumene hydroperoxide product is then cleaved.

The mixture of acetone and phenol is separated by distillation.

(a) What is the raw material and feedstock for benzene?

(b) Copy and complete the flow diagram below to summarise the manufacture of acetone from cumene.

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C2H4

HCl

CH2ClCH2Cl

CH2ClCH2Cl

CH3CH2Cl

C2H4 HCl O2 NaOH NaCl

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(c) Acetone can also be manufactured by oxidising propan-2-ol. In industry, several factors influence the decision as to which route might be used. Suggest two of these factors.

Percentage yield

5. Ethanol and ethanoic acid react to form the ester, ethyl ethanoate.

ethanol + ethanoic acid ethyl ethanoate + water

mass of one mole mass of one mole mass of one mole mass of one mole =56g =60g =88g =18g

Use the above information to calculate the percentage yield of ethyl ethanoate if 5.0g of ethanol produced 5.8g of ethyl ethanoate on reaction with excess ethanoic acid.

Show you working clearly.

6. In the reaction vessel, ethanol is produced in an exothermic reaction.

C2H4(g) + H2O(g) C2H5OH(g)

(a) What type of reaction is shown above (hint: think reactions of alkenes).

(b) If 1.64kg of ethanol (relative formula mass = 46) is produced from 10.0kg of ethane (relative formula mass = 28), calculate the percentage yield of ethanol.

7. One of the chemicals released in a bee sting is an ester that has the structure shown.

This ester can be produced by the reaction of an alcohol with an carboxylic acid.

If there is a 65% yield, calculate the mass of ester produced, in grams, when 4.0g of the alcohol reacts with a slight excess of the acid.

(Mass of one mole of the alcohol = 88g)(Mass of one mole of the ester = 130g)

Show you working clearly.

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8. Ammonia is produced in industry by the Haber Process.

N2(g) + 3H2(g) 2NH3(g)

Under certain conditions, 50okg of nitrogen reacts with excess hydrogen to produce 405g of ammonia.

Calculate the percentage yield of ammonia under these conditions.

Show you working clearly.

9. Sulfur trioxide can be prepared in the laboratory by the reaction of sulfur dioxide with oxygen.2SO2(g) + O2(g) 2SO3(g)

Under certain conditions, 43.2 tonnes of sulfur trixoxide are produced in the reaction of 51.2 tonnes of sulfur dioxide with excess oxygen.

Calculate the percentage yield of sulfur trioxide.

10. In the reaction shown below 7.2g of benzene (C6H6) produced 4.6g of methylbenzene (C7H8).

Benzene methylbenzene

Calculate the percentage yield of methylbenzene.

Molar volume

11. Calculate the volume occupied by:

(a) 11g of carbon dioxide, and(b) 6.4g of sulfur dioxide.

(Take the molar volume of each gas as 22.4 litres)

12. 1.1g of propane occupies 600cm3. Calculate the volume occupied by 1 mole of propane.

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+ CH3Cl + HCl

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13. The following results were obtained when an experiment was carried out to find th molar volume of nitrogen:

Capacity of flask = 100cm3

Mass of empty flask = 235.76gMass of flask + nitrogen = 235.88gLarge syringe reading before injection = 5cm3

Large syringe reading after injection = 89cm3

Use the above information to calculate the molar volume of nitrogen.

14. Calculate the volume of hydrogen released when 10g of calcium is added to excess water.

Ca(s) + 2H2O(l) Ca(OH)2(aq) + H2(g)

(Take the molar volume of hydrogen as 22 litres)

Atom economy

15. In industry, methanamide is produced by the reaction of an ester with ammonia.

Calculate the atom economy for the production of methanamide.

16. Aspirin, a common pain-killer, can be made by the reaction of salicylic acid withethanoic anhydride.

Calculate the atom economy for the formation of aspirin using this method.

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17. Sodium benzoate is used in the food industry as a preservative. It can be made by reacting benzoic acid with a concentrated solution of sodium carbonate.

Calculate the atom economy for the production of sodium benzoate.

Equations involving gaseous reactants (Gas composition)

18. CO(g) + 1/2O2(g) CO2(g)

Calculate the volume of oxygen required to react with 150cm3 of carbon monoxide.

19. CH4(g) + 2O2(g) CO2(g) + 2H2O(l)

Calculate the composition of the remaining gases when 30cm3 of methane burns in 40cm3 of oxygen at 20⁰C.

20. Name and give the volumes of the gases present after 20cm3 of ethane is exploded with 120cm3 of oxygen, under the following conditions:

(a) at 120⁰C and

(b) after bubbling through an alkali.

21. A mixture of 60cm3 of hydrogen and 40cm3 of carbon monoxide is passed over hot copper (II) oxide until no further reaction occurred.

(a) Write a balanced chemical equation for the reaction.

(b) Calculate the volume and composition of the resulting gas mixture.

22. The apparatus below can be used to determine the relative formula mass of liquids which are easily evaporated.

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Some of liquid X is injected into the large syringe and it evaporates.

The following results were obtained:

Mass of small syringe before injection = 5.744gMass of small syringe after injection = 5.648gLarge syringe before injection = 5cm3

Large syringe after injection = 89cm3

(a) Calculate the relative formula mass of liquid X.

(Take the molar volume of a gas to be 30.6 litres)

(b) Suggest why the above apparatus could not be used to determine the relative formula masses of liquids with boiling points above 100˚C.

23. Gas syringes are graduated to allow volumes of gases to be measured.

The heated box kept the syringe at a temperature greater that 100˚C. The syringe contained 150cm3 of hydrogen and 50cm3 of carbon monoxide mixed with 200cm3 of oxygen. When ignited, the gases reacted as shown.

CO(g) + 3H2(g) + 2O2(g) CO2(g) + 3H2O(g)

(a) Name the reactant gas which was in excess and give the remaining volume of this gas.

(b) What was the volume and composition of the products of the reaction?

(c) What would have been the reading on the gas syringe if, at the end of the reaction, the gases had been allowed to cool to room temperature?

Excess calculations

24. During a reaction 1g of magnesium was added to 30cm3 of hydrochloric acid, concentration 1 moll-1.

(a) Write a balanced chemical equation for the reaction described above.

(b) Calculate which reactant was in excess

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25. Calculate the mass of calcium sulfate formed when 10g of calcium carbonate is added to 200cm3 of excess hydrochloric acid.

26. 1.0g of zinc was placed in 20cm3 of 2 moll-1 hydrochloric acid. Calculate which reactant is in excess.

27. The equation for an experiment is shown.

Mg(s) + H2SO4(aq) MgSO4(aq) + H2(g)

The mass of magnesium used in the experiment was 0.50g and reacted with 100cm3, 0.1 moll-1. For this experiment, calculate the mass of magnesium, in grams, left unreacted.

Exam type questions (2014 – 2011)

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28.

29.

30.

31.

32.

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35. The overall equation for the fermentation of glucose is:

Calculate the percentage yield of ethanol if 445g of ethanol is produced from 1.0kg of glucose.

36. A chemical explosion is the result of a very rapid reaction that generates a large quantity of heat energy and, usually, a large quantity of gas.

The explosive RDX, C3H6N6O6, is used in the controlled demolition of disused buildings.

During the explosion it decomposes as shown.

C3H6N6O6(s) → 3CO(g) + 3H2O(g) + 3N2(g)

Calculate the volume of gas released when 1·0 g of RDX decomposes. (Take the molar volume to be 24 litres mol−1)

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33.

34.

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37. In the lab, methanamide can be prepared by the reaction of methanoic acid with ammonia.

When 1∙38 g of methanoic acid was reacted with excess ammonia, 0∙945 g of methanamide was produced.

Calculate the percentage yield of methanamide.Show your working clearly.

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Unit 3a: Getting the most from reactants Ink exercise

1. Read the passage below and answer the questions which follow:

(a) What evidence is there in the passage or flow diagram that the reaction in the reactor is exothermic.[1]

(b) From the flow diagram give a use for the heat released. [1]

(c) Why is the zinc considered to be a heterogeneous catalyst? [1]

(d) (i) What is happening at X in the flow diagram? [1]

(ii) Why is this an advantage? [1]

(e) Why can water and butan-2-ol not be separated by distillation? [1]

(f) Give three pieces of evidence from the passage that would suggest that the process is profitable.[1]

2. 280cm3 of carbon dioxide has a mass of 0.55g. Calculate the molar volume of carbon dioxide.[2]

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3. From the following data calculate the molecular weight of gas X.

Mass of plastic bottle empty = 112.80g

Mass of plastic bottle + gas X = 113.52g

Capacity of plastic bottle = 1 litre

Molar volume of gas X = 22 litres [2]

4. What volume of hydrogen gas would be released if 3.27g of zinc was added to excess hydrochloric acid? [2]

5. A mixture of 80cm3 of methane (CH4) and 150cm3 of oxygen was exploded.

(a) Write a balanced equation for the reaction.

(b) Calculate the composition of the remaining gases at 120˚C. [3]

After cooling the gas remaining was shaken with sodium hydroxide solution.

(c) Name the gas absorbed by the sodium hydroxide solution.

(d) What would be the final volume of gas. [2]

6. The ester, methyl ethanoate, was prepared from 0.32g of methanol reacting with excess ethanoic acid:

CH3OH + CH3COOH CH3COOCH3 + H2O

If 0.45g of methyl ethanoate formed, calculate the percentage yield. [2]

7. The production of iron in the blast furnace is represented by the following equation:

Fe2O3 + 3CO 2Fe + 3CO2

Calculate the atom economy for the reaction that takes place in the blast furnace. [2]

[ /22]

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