NYJC 2022 Prelim P4 Answers

[Turn over NANYANG JUNIOR COLLEGE JC2 PRACTICAL PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS 2 1 TUTOR CENTRE NUMBER S INDEX NUMBER CHEMISTRY 9729/04 Paper 4 Practical 18 August 2022 2 hour 30 minutes Candidates answer on the Question Paper Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Give details of the practical shift and laboratory, where appropriate, in the boxes provided. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. Shift You may lose marks if you do not show your working or if you do not use appropriate units. Qualitative Analysis Notes are printed on pages 19 and 20. Laboratory 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 1(a), (b)(i) [7] 2(d) [4] 1 / 17 1(b)(ii)-(v) [6] 2(e), (f) [3] 2 / 16 1(c) [4] 3(a),(c)-(d) [5] 3 /10 2(a) [5] 3(b) [5] 4 / 12 2(b), (c) [4] 4(a) & (b)-(c) [12] Total /55 This document consists of 18 printed pages and 2 blank pages.

2 H2 Chemistry 9729/04 NYJC J2/22 PX Answer all the questions in the spaces provided. 1 An investigation of the chemistry of some vanadium ions FA 1 is a solution of a dilute acid. FA 2 contains vanadate(V) ions, VO3−, of concentration 0.50 mol dm–3. Ammonium vanadate(V), NH4VO3, is a crystalline solid that is slightly yellow in colour. It has a relatively low solubility in water at room temperature. Vanadium, like all transition metals, is able to exhibit variable oxidat ion states in its compounds. You are provided with a solution, FA 2, which was produced by reacting NH4VO3 with aqueous sodium hydroxide. In this reaction, the anion remains unreacted. (a) Write an equation for the reaction between ammonium vanadate(V) and sodium hydroxide to produce FA 2. Describe how, using a simple chemical test, you can confirm that this reaction occurred during the preparation of FA 2. DO NOT carry out this test. equation ................................ ................................ ................................ ........... test ................................ ................................ ................................ ................... ................................ ................................ ................................ ..................... [1] NH4VO3 + NaOH → NaVO3 + H2O + NH3 or NH4+ + OH → H2O + NH3 Gas evolved turns damp red litmus paper blue. NH3 is evolved. 1 mark for both equation and test Relevant stand