A-LEVEL CHEMISTRY 7405/3 - CIE Notes

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Surname Other Names Centre Number Candidate Number Candidate Signature

A-LEVEL CHEMISTRY

Paper 3

7405/3

Wednesday 20 June 2018 Time allowed: 2 hours

Morning

At the top of the page, write your surname and other names, your centre number, your candidate number and add your signature.

[Turn over]

*jun187405301*

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For this paper you must have: ? the Periodic Table/Data Booklet,

provided as an insert (enclosed) ? a ruler with millimetre measurements ? a scientific calculator, which you are

expected to use where appropriate.

INSTRUCTIONS ? Use black ink or black ball-point pen. ? Answer ALL questions. ? You must answer the questions in the

spaces provided. Do NOT write 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.

*02*

3 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.

DO NOT TURN OVER UNTIL TOLD TO DO SO

*03*

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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

*04*

5 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 [Turn over]

*05*

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