Name: Block:

Page 4 of 8 csonn_l6_t1_blocktest

Section B: Answer all questions.

2

9701/22/M/J/15© UCLES 2015

Answer all the questions in the spaces provided.

1 (a) Chemists recognise that atoms are made of three types of particle.

Complete the following table with their names and properties.

name of particle relative mass relative charge

+1

1/1836

[3]

(b) Most elements exist naturally as a mixture of isotopes, each with their own relative isotopic mass. The mass spectrum of an element reveals the abundances of these isotopes, which can be used to calculate the relative atomic mass of the element.

Magnesium has three stable isotopes. Information about two of these isotopes is given.

isotope relativeisotopic mass

percentageabundance

24Mg 24.0 79.0

26Mg 26.0 11.0

(i) Defi ne the term relative isotopic mass.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) The relative atomic mass of magnesium is 24.3.

Calculate the percentage abundance and hence the relative isotopic mass of the third isotope of magnesium. Give your answer to three signifi cant fi gures

percentage abundance = .................................

isotopic mass = .................................[3]

Name: Block:

Page 5 of 8 csonn_l6_t1_blocktest

2) (a) Define the term relative atomic mass. [2]

(b) i) Give the symbols (showing the nucleon numbers and charges) of the following three particles.

particle protons neutrons electrons symbol Tick (if

applicable)

P 6 8 6

Q 7 7 10

R 8 7 7

ii) Use the Data Booklet to identify which are not the usual isotopes of the elements concerned.

Place a tick in the box provided above. [6]

2

9701/21/O/N/10© UCLES 2010

ForExaminer’s

Use

Answer all the questions in the space provided.

1 In 1814, Sir Humphrey Davy and Michael Faraday collected samples of a flammable gas, A, from the ground near Florence in Italy.

They analysed A which they found to be a hydrocarbon. Further experiments were then carried out to determine the molecular formula of A.

(a) What is meant by the term molecular formula?

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [2]

Davy and Faraday deduced the formula of A by exploding it with an excess of oxygen and analysing the products of combustion.

(b) Complete and balance the following equation for the complete combustion of a hydrocarbon with the formula CxHy .

CxHy + (x + y4)O2 ................................ + ................................

[2]

(c) When 10 cm3 of A was mixed at room temperature with 50 cm3 of oxygen (an excess) and exploded, 40 cm3 of gas remained after cooling the apparatus to room temperature and pressure.

When this 40 cm3 of gas was shaken with an excess of aqueous potassium hydroxide, KOH, 30 cm3 of gas still remained.

(i) What is the identity of the 30 cm3 of gas that remained at the end of the experiment?

...................................................

(ii) The combustion of A produced a gas that reacted with the KOH(aq).

What is the identity of this gas?

...................................................

(iii) What volume of the gas you have identified in (ii) was produced by the combustion of A?

...............................cm3

(iv) What volume of oxygen was used up in the combustion of A?

...............................cm3 [4]

Name: Block:

Page 6 of 8 csonn_l6_t1_blocktest

2

9701/21/O/N/10© UCLES 2010

ForExaminer’s

Use

Answer all the questions in the space provided.

1 In 1814, Sir Humphrey Davy and Michael Faraday collected samples of a flammable gas, A, from the ground near Florence in Italy.

They analysed A which they found to be a hydrocarbon. Further experiments were then carried out to determine the molecular formula of A.

(a) What is meant by the term molecular formula?

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [2]

Davy and Faraday deduced the formula of A by exploding it with an excess of oxygen and analysing the products of combustion.

(b) Complete and balance the following equation for the complete combustion of a hydrocarbon with the formula CxHy .

CxHy + (x + y4)O2 ................................ + ................................

[2]

(c) When 10 cm3 of A was mixed at room temperature with 50 cm3 of oxygen (an excess) and exploded, 40 cm3 of gas remained after cooling the apparatus to room temperature and pressure.

When this 40 cm3 of gas was shaken with an excess of aqueous potassium hydroxide, KOH, 30 cm3 of gas still remained.

(i) What is the identity of the 30 cm3 of gas that remained at the end of the experiment?

...................................................

(ii) The combustion of A produced a gas that reacted with the KOH(aq).

What is the identity of this gas?

...................................................

(iii) What volume of the gas you have identified in (ii) was produced by the combustion of A?

...............................cm3

(iv) What volume of oxygen was used up in the combustion of A?

...............................cm3 [4]3

9701/21/O/N/10© UCLES 2010 [Turn over

ForExaminer’s

Use

(d) Use your equation in (b) and your results from (c)(iii) and (c)(iv) to calculate the molecular formula of A.

Show all of your working.

[3]

[Total: 11]

Name: Block:

Page 7 of 8 csonn_l6_t1_blocktest

�85 Ammonium sulfate, (NH4)2SO4, is widely used as a fertiliser.

In order to find the percentage of ammonium sulfate in the fertiliser, a sample of the fertiliser was analysed by reacting a known amount with an excess of KOH(aq) and then titrating the unreacted KOH with dilute HCl.

(a) Ammonium sulfate reacts with KOH. Complete and balance the chemical equation for this reaction.

(NH4)2SO4 + …….KOH —> …….NH3 + ………. + ………

(b) 6.60 g of a fertiliser containing ammonium sulfate was boiled with an excess of KOH(aq). All of the ammonia gas liberated was absorbed in 50.0 cm3 of 1.00 mol dm-3 HCl (an excess).

NH3 + HCl —> NH4Cl

The resulting solution was diluted carefully to exactly 250 cm3 to give a solution of suitable concentration for titration.

A 25.0 cm3 portion of this solution was titrated with 0.100 mol dm-3 KOH solution. 20.0 cm3 of KOH solution was required for neutralisation. KOH + HCl —> KCl + H2O

i) Calculate the amount, in moles, of KOH in 20.0 cm3 of the KOH solution.

ii) Calculate the amount, in moles of HCl in the 25.0 cm3 that was titrated with KOH in (i).

iii) Use your answer to (ii) to calculate the amount, in moles of HCl in the total 250 cm3 solution.

Name: Block:

Page 8 of 8 csonn_l6_t1_blocktest

�9iv) Calculate the amount, in moles of HCl, initially in the 50.0 cm3 of 1.00 mol dm-3 HCl.

v) Use your answers to (iii) and (iv) to calculate the amount, in moles of HCl used up by the ammonia.

vi) The number of moles of NH3 produced is the same as the number of moles of HCl calculated in (v). Using the correct equation given above, and your answer to (v), calculate the number of moles of (NH4)2SO4 reacted.

vii) Use your answer to (vi) to calculate the mass of (NH4)2SO4 in the fertiliser. [Mr of (NH4)2SO4 is 132.1]

viii) Hence, calculate the percentage purity of the ammonium sulfate fertiliser.

[Total: 10]