MJC H2 Chem 2013 Prelim P2 QP

Name _______________________ Class: ___________ Reg Number: ______ MERIDIAN JUNIOR COLLEGE Preliminary Examination Higher 2 ____________________________________________________________________________ Chemistry 9647 Paper 2 Structured Questions 19 September 2013 2 hours Additional Materials: Data Booklet ____________________________________________________________________________ INSTRUCTIONS TO CANDIDATES   Write your name, class and register number in the spaces provided at the top of this page. Write your calculator brand and model/number in the box provided above. Answer all questions in the spaces provided on the question paper. All working must be shown clearly. INFORMATION FOR CANDIDATES This document consists of 26 printed pages and 2 blank pages   ©chemistry@meridian jc Examiner’s Use Paper 1 MCQ / 40 Paper 2 Q1 / 12 Q2 / 9 Q3 / 15 Q4 / 12 Q5 / 10 Q6 / 14 / 72 Paper 3 / 80 Total / 192 % & Grade The number of marks is given in brackets [ ] at the end of each question or part question. You are reminded of the need for good English and clear presentation in your answers. Calculator Model / No. 890

1 ©chemistry@meridian jc   [Turn over  1 Planning (P) You are to design an experiment to determine the enthalpy change of the reaction of magnesium with sulfuric acid as follows: Mg (s) + H2SO4 (aq)  MgSO4 (aq) + H2 (g) H1 You are provided with the following information and a list of apparatus and reagents. You may also use other apparatus normally found in a school laboratory. Reagents and apparatus:  1.0 mol dm 3 H2SO4  Mg turnings  A thermometer with 0.2 C division  A 200 cm 3 styrofoam cup Assume that 4.18 J is required to raise the temperature of 1 cm 3 of any solution by 1 oC. (a) (i) The enthalpy change of reaction bet ween magnesium and sulfuric acid is determined to be approximately 140 kJ mol 1. A student attempted to plan the experiment and s uggested the use of 100 cm 3 of sulfuric acid with 0.1 g of Mg turnings but was told by his teacher that the quantity of Mg used was inappropriate.   Explain with the aid of suitable calc ulations why the quantity of Mg suggested was inappropriate. [2] 891

2 ©chemistry@meridian jc   [Turn over  (ii) Hence, write a detailed plan to veri fy the enthalpy change of reaction between magnesium and sulfuric acid, H1. Your plan should include the following:  Justification of the mass of Mg turnings to be used  Tabulation of raw data  Brief description of how the data can be used to determine the enthalpy change of reaction [6] 892

3 ©chemistry@meridian jc   [Turn over  (b) The standard enthalpy change of formation of magnesium oxide, Hf cannot be determined directly by experiment and is determined via an indirect approach using Hess’ Law