This document contains 2022

AQA A LEVEL CHEMISTRY Paper 3 2022 BUNDLE

7405/3

Question Paper + Mark Scheme 2022

Section A box

Answer all questions in this section.

0 1 A value for enthalpy of solution can be determined in two ways:

• from a cycle, using lattice enthalpy and enthalpies of hydration

• from the results of a calorimetry experiment.

0 1 . 1 Define the term enthalpy of lattice dissociation.

[2 marks]

0 1 . 2 The enthalpy of solution for ammonium nitrate is the enthalpy change for the reaction

shown.

NH4NO3(s) + aq → NH4

+

(aq) + NO3

−

(aq) ∆H = +26 kJ mol−1

Table 1

NH4

+

(g) NO3

−

(g)

Enthalpy of hydration hydH/ kJ mol 1 −307 −314

Draw a suitably labelled cycle and use it, with data from Table 1, to calculate the

enthalpy of lattice dissociation for ammonium nitrate.

[3 marks]

Enthalpy of lattice dissociation kJ mol−1

4

*04*

IB/M/Jun22/7405/3

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outside the

box 0 1 . 3 A student does an experiment to determine a value for the enthalpy of solution for

ammonium nitrate.

The student uses this method.

• Measure 25.0 cm3 of distilled water in a measuring cylinder.

• Pour the water into a beaker.

• Record the temperature of the water in the beaker.

• Add 4.00 g of solid NH4NO3 to the water in the beaker.

• Stir the solution and record the lowest temperature reached.

Table 2 shows the student’s results.

Table 2

Initial temperature / °C 20.2

Lowest temperature / °C 12.2

Calculate the enthalpy of solution, in kJ mol−1, for ammonium nitrate in this

experiment.

Assume that the specific heat capacity of the solution, c = 4.18 JK−1 g−1

Assume that the density of the solution = 1.00 gcm−3

[3 marks]

Enthalpy of solution kJ mol−1

5

*05*

Turn over ►

IB/M/Jun22/7405/3

Do not write

outside the

box 0 1 . 4 The uncertainty in each of the temperature readings from the thermometer used in

this experiment is ±0.1°C

Calculate the percentage uncertainty in the temperature change in this experiment.

[1 mark