AQA A-Level Chemistry Paper 3 Predicted Paper 2023 questions and answers

AQA

A-Level Chemistry 

Paper 3

Predicted Paper 2023

Name ……………………………………………………………………

Date …………………

2 hours allowed

You should have access to the AQA insert (periodic table and data sheet) to help with answering the questions.

Grade boundaries

These are VERY rough guesses! Getting a C on this paper does not guarantee you the same mark in the exam.

• A* - 90

• A – 80

• B – 70

• C – 60

• D – 50

• E - 40

SECTION A

01

A sample of hydrated K2SO4 (K2SO4.????H2O) with a mass of 2.458 g was heated to remove all water of crystallisation. The solid remaining had a mass of 1.515 g.

(The molar mass of the remaining solid was 174.26 gmol-1)

01.1 Determine a possible formula of the hydrated potassium salt. Your answer must show relevant working.

[3 marks]

01.2 Suggest how a student doing this experiment could check that all water had been removed.

[1 mark]

01.3 The entropy change of hydration of K2SO4 is + 225 JK-1mol-1

i) Suggest in terms of the states of the particles involved, why this entropy change is positive.

[1 mark]

ii) Explain why K2SO4 dissolves in water at 25°C, despite the enthalpy change of solution being endothermic.

ΔH = +24 kJmol-1

[2 marks]

02

A student wants to investigate the kinetics of the reaction between hydrogen peroxide and iodide ions in the presence of sulfuric acid.

Rate = [H2O2]x[I-]y

02.1 Write the balanced chemical equation for the reaction between hydrogen peroxide and iodide ions.

[Include state symbols]

[2 marks]

02.2 The concentration of hydrogen peroxide is measure at different time intervals while keeping the concentration of iodide and H+ ions constant. The student could obtain the following results.

t/ 103 s [H2O2]/moldm-

3

0 0.20

2 0.14

4 0.09

6 0.06

8 0.04

10 0.03

i) Plot the graph of [H2O2]/ moldm-3 against / 103 s

[2 marks]

ii) Deduce the order of the reaction with respect to hydrogen peroxide (find the value of x).

[1 mark]

02.3 The experiment was repeated using an initial rate method.

Experiment [H2O2]/

moldm-3 [I-]/

moldm-3 Initial rate

/moldm-3s-1

1 0.2 0.50 2.95×10-5

2 0.05 1.00 2.36×10-5

3 0.04 0.50 9.44×10-6

4 0.05 2.00 4.72×10-5

Determine the order with respect to I- (find the value of y).

[2 marks]

02.4 Write the rate equation for the above reaction.

[1 mark]

02.5 Calculate the rate constant for this reaction by using the data from experiment 2.