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AQA A-LEVEL CHEMISTRY PAPER 3 VERSION 1

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AQA A-LEVEL CHEMISTRY PAPER 3 VERSION 1 AQA A-LEVEL CHEMISTRY PAPER 3 VERSION 1 A-level CHEMISTRY Paper 3 Wednesday 20 June 2018 Morning Time allowed: 2 hours Materials For this paper you must have: • the Periodic Table/Data Booklet, provided as an insert (enclo...

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  • May 30, 2022
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AQA A-LEVEL CHEMISTRY PAPER 3 VERSION 1



Please write clearly in block capitals.


Centre Candidate
number number


Surname

Forename(s)

Candidate ure



A-level
CHEMISTRY
Paper 3


Wednesday 20 June 2018 Morning Time allowed: 2 hours
Materials For Examiner’s Use
For this paper you must have:
 the Periodic Table/Data Booklet, provided as an insert (enclosed) Question Mark
 a ruler with millimetre measurements 1
 a scientific calculator, which you are expected to use where appropriate. 2
3
Instructions
 Use black ink or black ball-point pen. 4
 Fill in the boxes at the top of the page. Section
 Answer all questions. B
 You must answer the questions in the spaces provided. Do not TOTAL
write outside the box around each page or on blank pages.
 All working must be shown.
 Do all rough work in this book. Cross through any work you do not
want to be marked.

Information
 The marks for questions are shown in brackets.
 The maximum mark for this paper is 90.

Advice
 You are advised to spend about 70 minutes on Section A and 50 minutes on Section B.

,*jun1 7405301*
IB/M/Jun18/E10 7405/3

, Donot
Do not
2 write
write
outsidethe
outside the
box
box


Section A

Answer all questions in this section.


0 1 Iodide ions are oxidised to iodine by hydrogen peroxide in acidic conditions.

H2O2(aq) + 2H+(aq) + 2I–(aq)  I2(aq) + 2H2O(l)

The rate equation for this reaction can be written as

rate = k [H2O2]a [I–]b [H+]c

In an experiment to determine the order with respect to H +(aq), a
reaction mixture is made containing H+(aq) with a concentration of 0.500
mol dm–3

A large excess of both H2O2 and I– is used in this reaction mixture so
that the rate equation can be simplified to

rate = k1 [H+]c

0 1 .1 Explain why the use of a large excess of H 2O2 and I– means that the rate of
reaction at a fixed temperature depends only on the concentration of H+
(aq).
[2 marks]




0 1 .2 Samples of the reaction mixture are removed at timed intervals and
titrated with alkali to determine the concentration of H+(aq).

State and explain what must be done to each sample before it is titrated with alkali.
[2 marks]




*02
IB/M/
* Jun18/7405/3

, Do not
3 write
outside the
box


0 1 .3 A graph of the results is shown in Figure 1.

Figure 1




Explain how the graph shows that the order with respect to H+(aq) is zero.
[2 marks]




0 1 .4 Use the graph in Figure 1 to calculate the
value of k1
Give the units of k1 [3 marks]




k1

Units

Turn over ►

*03
IB/M/
* Jun18/7405/3

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