NYJC 2024 H2 Chem P4 Solutions

H NANYANG JUNIOR COLLEGE JC2 PRACTICAL PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS CENTRE NUMBER S INDEX NUMBER CHEMISTRY 9729/04 Paper 4 Practical 14 August 2024 2 hour 30 minutes Candidates answer on the Question Paper Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your Centre number, index number, 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 23 and 24. 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 / 16 2 / 16 3 /12 4 / 11 Total /55 This document consists of 20 printed pages and 4 blank pages.

2 H2 Chemistry 9729/04 NYJC J2/24 PX Answer all questions in the space provided. 1 An investigation of a gemstone Spinel minerals form crystals that are often used as gemstones. The general formula of a spinel mineral is AB2O4, where A and B are different metal ions. The presence of different combinations of metal ions accounts for the range of colours found in these gemstones. One example of a spinel gemstone is hercynite, which is blue-green in colour. As they are essentially composed of metal oxides, spinel crystals may be reacted with strong acids to form solutions containing salts of the metal ions present. The rarity and high cost of spinel gemstones, however, prohibit the preparation of such solutions for this task. The FA 1 solution you are supplied with is a mixture of two salts. It is intended to duplicate a solution that could have been produced by reacting hercynite crystals with a strong mineral acid. Clearly, non-metal ions are also present in FA 1. FA 1 is a solution containing the metal ions, A and B, together with non-metal ions. FA 2 is sodium carbonate, Na2CO3. Solid FA 3 is granulated zinc. You will perform tests to identify the metal ions, A and B, present in FA 1. You are not expected to identify the anions. You are advised to consider the general formula of the spinel minerals, AB2O4, and the likely oxidation states of the metal ions, A and B, before you start this experiment. Unless otherwise stated, the volumes given below are approximate and should be estimated rather than measured. Test and identify any gases evolved. (a) Carry ou