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

4 5 Chromium and its compounds undergo the following reactions. N has the following composition by mass: Cr, 15.5%; S, 38.1%; N, 29.2%. Which of the following can be deduced from the above reaction scheme? A The values of x and y in N are 4 and 2 respectively. B The types of reactions that occur are ligand exchange and redox only. C The formula of K is Cr(OH) 2(H2O)6. D H2O2 is a reducing agent in the conversion of K to L. 6 Which one of the following statements about Group 2 elements and their compounds is correct? A Beryllium chloride has a higher boiling point than magnesium chloride as it has a more exothermic lattice energy than magnesium chloride. B The reducing power of Group 2 elements increases down the group. C 1 mole of barium carbonate, on heating over a short period of time, decomposes to give more carbon dioxide gas than 1 mole of magnesium carbonate. D Barium has a higher melting point than magnesium due to more electrons. 7 Liquefaction can be defined as a process that generates a liquid from a gas and this can be done by altering pressure. In the liquefaction of CH4 and NH3, the pressure needed for NH3 is less than CH4. Which of the following reasons best explains this observation? A NH3 has stronger intermolecular forces of attraction than CH4. B NH3 has weaker bond energy than CH4. C NH3 molecules are bigger than CH4 molecules. D NH3 molecules possess less kinetic energy than CH4 molecules. Cr2(SO4)3 K green solution L yellow NaOH (aq) in excess H2O2 M orange H+ NH4SCN N NH4[Cr(SCN)x(NH3)y]

5 [Please Turn Over 8 Phosphate buffers are commonly used in biological chemistry research. H2PO4– ⇌ HPO42– + H+ p Ka = 6.7 A phosphate buffer with pH 7.4 was prepared using NaH2PO4 and Na2HPO4 solutions. The total hydrogen phosphates concentration ([HPO 42–] + [H 2PO4–]) of the buffer was 0.3 mol dm–3. What are the concentrations of NaH2PO4 and Na2HPO4 used to create this buffer? [NaH2PO4] / mol dm–3 [Na2HPO4] / mol dm–3 A 0.23 0.07 B 0.07 0.23 C 0.10 0.50 D 0.05 0.25 9 Cyproterone acetate (CPA) is a drug that is used in the treatment of prostate cancer. CPA Which of the following statements about CPA are incorrect? 1 One mole of silver is formed when one mole of CPA is warmed with [Ag(NH 3)2]+. 2 Two moles of yellow precipitate is formed when one mole of CPA is warmed with alkaline iodine solution. 3 One mole of silver chloride is formed when one mole of CPA is heated with ethanolic silver nitrate. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2 and 3

6 10 Consider the following equilibrium: When Q2 is allowed to react with R 2 in a molar ratio of 2:1 at a total initial pressure of 3 atm, 20% of the equilibrium mixture is found to be Q2R. What is the equilibrium constant, Kp, of this reaction? A 0.0174 atm−1 B 0.0781 atm−1 C 0.194 atm−1 D 0.232 atm−1 11 Use of the Data Booklet is relevant to this question. Iodine clock reaction can be used to study how the concentration of iodide ions affect the rate of oxidation of iodide ions with perox odisulfate ions. Peroxodisulfate ions convert iodide ions into iodine slowly. S2O82−(aq) + 2I−(aq) →2SO42−(aq) + I2(aq) The rate of the reaction can be increased by the addition of catalysts such as aqueous iron (III) ions. A possible catalysed reaction pathway involves the following steps: Step 1: 2Fe3+(aq) + 2I −(aq) → I2(aq) + 2Fe2+(aq) Step 2: S2O82−(aq) + 2Fe2+(aq) → 2SO42−(aq) + 2Fe3+(aq) Which of the following statements are correct? 1 Aqueous cobalt( II) ions can be used as a catalyst in this reaction. 2 S2O82− is a stronger oxidising agent than Fe3+. 3 The Ecell ⦵ for step 2 is more positive than step 1. A 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3

7 [Please Turn Over 12 Which of the following reactions has no change in the hybridisation state of the carbon atom indicated with an asterisk (*) from the reactant to the intermediate in the mechanism? A B C D 13 What is the volume of vapour formed when 10 cm3 of liquid ethanol (density: 0.789 g cm−3) is heated to 300 °C at a pressure of 5 bar? A 85.5 cm3 B 855 cm3 C 163.3 cm3 D 1633 cm3

8 14 Which compounds liberate carbon dioxide gas when heated with acidified potassium manganate(VII)? 1 2 3 A 1 and 2 only B 2 and 3 only C 1, 2 and 3 D None of the above 15 Trifluorooxonium has the formula OF3n+ and its shape is trigonal pyramidal. What is the value of n in trifluorooxonium? A 1 B 2 C 3 D 4 16 Use of the Data Booklet is relevant to this question. Which set of reagents, when added in the order shown below, would convert Fe 3+(aq) to [Fe(CN)6]3−(aq)? step 1 step 2 step 3 A Zn(s) CN −(aq) SO 2(g) B I−(aq) CN−(aq) Cl2(g) C H2O2(aq) I−(aq) CN−(aq)