2019 RVHS Prelim P3 QP

River Valley High School 9729/03/PRELIM/19 [Turn over 2019 Preliminary Examination RIVER VALLEY HIGH SCHOOL JC2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS 18J CENTRE NUMBER S INDEX NUMBER H2 CHEMISTRY 9729/03 Paper 3 Free Response 24 September 2019 2 hours Candidates answer on separate paper. Additional Materials: Answer Booklet Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class, centre number and index number on all the work you hand in. Write in dark blue or black pen on both sides of paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer one question. Begin each question on a fresh page. A Data Booklet is provided. Do not write anything on it. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. This document consists of 15 printed pages and 1 blank page. Section A

2 River Valley High School 9729/03/PRELIM/19 2019 Preliminary Examination Answer all the questions from this section. 1 (a) (i) Hydrogen halide, HX, is soluble in both polar and nonpolar solvents. Describe the interactions formed when HX dissolves in polar solvents such as water. [1] (ii) The boiling point s of the first four hydrogen halides down Group 17 are listed in the following table. Table 1.1 Hydrogen Halide Boiling Point / °C HF 20 HCl −85 HBr −67 HI −35 Describe and explain the trend. [2] (iii) Four gas jars containing a hydrogen halide from Table 1.1 were prepared. When a red-hot steel needle is introduced to the gas jars respectively, two of them showed intense colour changes while the other two showed no visible change. With reference to the Data Booklet, describe and explain the observations. [3] (b) (i) In an experiment, an excess of 5.00 g AgCl(s) was added to 1 dm3 solution of 0.00100 mol dm–3 NaCl and allowed to reach equilibrium at 298 K. The mixture was then filtered and the residue was dried thoroughly. 100 cm3 of the filtrate required the addition of 4.00  10–12 mol of NaBr for the first trace of AgBr to appear. Given that solubility of Ag Br in water is 0.140 mg L–1, calculate the concentration of Ag+ ions in the 100 cm3 filtrate. [2] (ii) Calculate the solubility of AgCl in mol dm–3. [2] (iii) Calculate the mass of residue collected from the filtration. [1]

3 River Valley High School 9729/03/PRELIM/19 [Turn over 2019 Preliminary Examination (c) (i) There are two possible intermediates for Reaction I. Draw the structure of the more stable intermediate and explain its stability. [2] (ii) Describe the mechanism of R eac