ASRJC 2021 J2Prelims H2Chem P4 QP

ASRJC JC2 PRELIM 2021 9729/04/H2 [Turn Over ANDERSON SERANGOON JUNIOR COLLEGE 2021 JC 2 PRELIMINARY EXAMINATION NAME:________________________________ ( ) CLASS: 21 /____ CHEMISTRY 9729/04 Paper 4 Practical 26 August 2021 2 hours 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your name, class and index number 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 a 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. You may lose marks if you do not show your working or if you do not use appropriate units. Quantitative Analysis Notes are printed on pages 27 and 28. Shift 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 / 13 2 / 10 3 / 18 4 / 14 Total / 55 This document consists of 26 printed pages and 2 blank pages.

2 ASRJC JC2 PRELIM 2021 9729/04/H2 Answer all the questions in the spaces provided. 1 Determination of enthalpy change of reaction FA 1 is solid potassium hydrogencarbonate, KHCO3 FA 2 is 1.50 mol dm–3 sulfuric acid, H2SO4 (I) KHCO3(s) + aq ® K+(aq) + HCO3–(aq) DHsol(KHCO3) The molar enthalpy change of solution of solid potassium hydrogencarbonate is the enthalpy change when one mole of solid potassium hydrogencarbonate dissolves in sufficient water such that the ions are well separated as shown in (I). When added to water, solid potassium hydrogencarbonate quickly dissolves and the temperature of the mixture falls. (II) KHCO3(aq) + ½H2SO4(aq) ® ½K2SO4(aq) + H2O(l) + CO2(g) DHr(KHCO3(aq)) The molar enthalpy change of reaction of aqueous potassium hydrogencarbonate with sulfuric acid in (II) is the enthalpy change when one mole of aqueous potassium hydrogencarbonate reacts with excess sulfuric acid. You are to perform experiments by which you will determine the enthalpy change DHsol(KHCO3). You will also determine the enthalpy change DHr(KHCO3(aq)) using the data provided before using your results in a Hess’s Law calculation.

3 ASRJC JC2 PRELIM 2021 9729/04/H2 [Turn Over (a) Follow the instructions below to determine the maximum temperature change when a known mass of solid potassium hydrogencarbonate, FA 1, dissolves completely in water. In an appropriate format in the space provided below, record • all weighings to an appropriate level of precision, • all values of temperature to an appropriate level of precision. 1. Weigh the capped bottle containing FA 1. 2. Place one polystyrene cup inside a second polystyrene cup.