This document consists of 8 printed pages.
SP (CW) S76396
© UCLES 2004
UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
Joint Examination for the School Certificate
and General Certificate of Education Ordinary Level
Paper 3 Practical Test
1 hour 30 minutes
Candidates answer on the Question Paper.
Additional Materials: as listed in Instructions to Supervisors
READ THESE INSTRUCTIONS FIRST
Write your name, Centre number and candidate number in the spaces at the top of this page.
Answer both questions.
Write your answers in the spaces provided on the question paper.
You should show the essential steps in any calculation and record all experimental results in the spaces
provided on the question paper.
If you are using semi-micro methods in Question 2, you should modify the instructions to suit the size of
apparatus and the techniques you are using.
The number of marks is given in brackets [ ] at the end of each question or part question.
Qualitative Analysis notes are printed on page 8.
For Examiner’s Use
If you have been given a label, look at the
details. If any details are incorrect or
missing, please fill in your correct details
in the space given at the top of this page.
Stick your personal label here, if
Solution P was prepared by dissolving 3.30 g of a compound M IO3 in 1.00 dm
3 of water. An
acidified solution of M IO3 oxidises potassium iodide to iodine which can be titrated with
M IO3 + 5I
– + 6H+ → M+ + 3I2 + 3H2O
I2 + 2S2O3
2– → 2I– + S4O62–
You are to determine the relative molecular mass of M IO3 and hence identify M.
Q is 0.100 mol/dm3 sodium thiosulphate.
(a) Put Q into the burette.
Pipette a 25.0 cm3 (or 20.0 cm3) portion of P into a flask and add about a test-tubeful of
dilute sulphuric acid followed by about a test-tubeful of aqueous potassium iodide. The
solution should turn red-brown. Do not add the starch indicator at this stage.
Add Q from t