SRJC_2008 JC2 Prelim H2 Paper 2

© SRJC 2008 9746/02/Prelims/2008 [Turn Over SERANGOON JUNIOR COLLEGE General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9746/02 Preliminary Examination 25 August 2008 Paper 2 1 hr 30 min Additional Materials: Data Booklet Writing Papers READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough work. Answer all questions in the space provided. At the end of the examination, fasten all your work securely together. The number of marks is given in the brackets [ ] at the end of each question or part questions. For Examiner’s Use 1 2 3 4 5 Total This document consist of 12 printed pages and 0 blank page

2 © SRJC 2008 9746/02/Prelims/2008 [Turn Over 1 Potassium manganate (VII) is an oxidising agent used in redox titrations. A 50.0 cm 3 sample of iron ( II) oxalate, FeC 2O4, was dissolved in water and the solution made up to 250 cm 3. A 25.0 cm 3 portion of this solution was acidified and titrated with 20.80 cm3 of 0.025 mol dm-3 potassium manganate (VII). (a) (i) State the change in oxidation number for manganese. (ii) Write an ionic equation for the oxidation of oxalate ion to carbon dioxide. (iii) Write an overall equation for the reaction between potassium manganate (VII) and iron (II) oxalate. (iv) Calculate the concentration of iron (II) oxalate in the original sample. (v) State the colour change at t he end point of the titration. [5]

3 © SRJC 2008 9746/02/Prelims/2008 [Turn Over In the above redox titration, carbon dioxid e gas is produced. One of the uses of carbon dioxide is in the manufacture of carbonated drinks. Cola, a carbonated drink, was originally invented by chemist, John Pemberton, to stop headaches and calm nervousness. Cylinders of pressurised carbon dioxi de are used to produce cola. A commercial cola drink was manufactured using such cylinde rs, each with internal volume of 5 dm 3 and contains 2.58 kg of carbon dioxi de. The pressure inside each of the cylinder was found to be 1.0 x 104 kPa at room temperature. A glass of cola is fizzy because carbon dioxide has been dissolved in it under pressure. When 500 cm 3 of commercial cola drink is poured out from a bottle, the carbon dioxide is gradually released as bubbles of gas .