SAJC Prelim P1_QP

1 [Please Turn Over NAME Class ST ANDREW’S JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION Chemistry (9729) Paper 1 Multiple Choice 17 September 2018 1 hour Additional Materials: Multiple Choice Answer Sheet, Data Booklet READ THESE INSTRUCTIONS: Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer sheet. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. This document consists of 14 printed pages.

2 1 To identify an oxide of nitrogen, the oxide is mixed with an excess of hydrogen and passed over a catalyst at a suitable temperature. The water collected weighs 0.133 g. The ammonia produced is neutralised by 18.50 cm3 of 0.2 mol dm-3 HCl. Which of the following could be the oxide? 1 N 2O 2 NO 2 3 NO 3 4 N 2O4 A 3 only B 1 and 2 only C 2 and 3 only D 2 and 4 only 2 This question is about sparingly soluble salts. AgCl Ag I Hg I2 Ksp 1.0 × 10−10 8.3 × 10−16 1.1 × 10−21 From the above information, which statements are not true? A For a solution containing 1 mol dm −3 of NaC l and Na I, the concentration of chloride ions when AgI just starts to precipitate is 1 mol dm−3. B The solubility of HgI2 is 6.50 × 10−8 mol dm−3. C The solubility of HgI2 is the lowest. D The units for Ksp for HgI2 is mol3 dm−9.

3 [Please Turn Over 3 The following tests were performed on an aqueous solution containing bromide and iodide ions. Step Test Observations 1 Add excess AgNO 3(aq). A mixture of cream and yellow precipitate were formed. 2 To the mixture from step 1, add concentrated NH3. The cream precipitate dissolved to form a colourless solution. The yellow precipitate was insoluble. 3 Filter the mixture from step 2. Filtrate was a colourless solution. Residue was a yellow solid. 4 Add Cl2(aq) to filtrate. Brown solution is formed. Which of the following statements is correct? A In step 2, the cream precipitate dissolved because the addition of concentrated NH3 results in formation of a complex which decreases the Ksp of AgBr. B In step 2, the yellow precipitate was insoluble because the Ksp of AgI is higher than the Ksp of AgBr. C In step 2, the yellow precipitate was insoluble because the ionic product of Ag I is higher than the Ksp of AgI. D In step 4, a disproportionation reaction has taken place. 4 A stable ion of Q has the following properties: • has a noble gas configuration • has more protons than electrons • was obtained by removing electrons from the same orbital Which of the following could be Q? A Al B Ca C Cu D S