H1 Paper 2 (Student Copy)

Name and Form Class Index Number Subject Tutor ANGLO-CHINESE JUNIOR COLLEGE DEPARTMENT OF CHEMISTRY Preliminary Examination CHEMISTRY 8872/02 Higher 1 Paper 2 22 August 2012 2 hours Candidates answer Section A on the Question Paper. Additional Materials: Writing Paper Data Booklet READ THESE INSTRUCTIONS FIRST Write your index number and name on all the work yo u hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs or ro ugh working. Do not use staples, paper clips, highlighters, glue or correction fluids. Section A Answer all questions Section B Answer two questions on separate answer paper. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A B5 B6 B7 Total This document consists of 16 printed pages. 8872/Prelims/12 ANGLO-CHINESE JUNIOR COLLEGE © ACJC 2012 Department of Chemistry [Turn over

© ACJC 2007 9746/01/Prelim/07 2 Section A Answer all questions in this section in the spaces provided 1 (a) In an attempt to determine the hydroxide concentrat ion in a titration procedure, a student filled up the burette with sod ium chloride instead of hydrochloric acid and starts the titration. He real ised something was amiss when the methyl orange indicator did not show any colour change. If he had correctly filled the burette with hydroch loric acid and carried out the titration, what is the expected colour change at the end point? ……………………………………………………………………………………. [1] For Examiner’s use (b) The student pipetted a 50.0 cm 3 sample containing sodium chloride and sodium hydroxide which he had wrongly prepared in (a) , and titrated it with hydrochloric acid. The end point was reached w hen 13.00 cm 3 of 0.35 mol dm -3 of hydrochloric acid was added. Calculate the concentration of sodium hydroxide present in the 50.0 cm 3 sample. [1] (c) 22.00 cm 3 of 0.45 mol dm -3 of acidified KMnO 4 was added in excess to oxidise the chloride ions present in (b) . The excess KMnO 4 required 14.80 cm 3 of 0.60 mol dm -3 of hydrogen peroxide solution for complete reaction. (i) KMnO 4 undergoes a redox reaction with H 2O2. Define the terms in italics. …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… (ii) Write the half equation for the oxidation of hydrog en peroxide to oxygen, and hence the overall balanced equation for the reaction For Examiner’s

© ACJC 2007 9746/01/Prelim/07 [Turn over 3 between acidified KMnO 4 and hydrogen peroxide. use (iii) Calculate t