MI H2 Chem 2013 Prelim P2 QP

Class Adm No Candidate Name: This document consists of 18 printed pages. [Turn over 2013 Preliminary Examination II Pre-university 3 H2 CHEMISTRY 9647/02 Paper 2 Structured Questions Wednesday, 18 Sep 2013 2 hours Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and index number in the spaces provided at the top of this page. Write in dark blue or black pen in the spaces provided. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. A Data Booklet is provided. 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. For Examiner’s Use 1 /12 2 /10 3 /13 4 /12 5 /13 6 /12 Total /72 804

2 1 Planning (P) For Examiner’s Use You are to design an experiment to determine the enthalpy change of reaction between solid Mg(OH)2 and hydrochloric acid. You are provided with the following list of apparatus and reagents. [You may assume that all other common laboratory apparatus not listed below are also available.] Reagents:  FA1: 2.50 mol dm -3 of HCl  FA2: Mg(OH)2 solid Apparatus:  A thermometer with 0.2 °C interval  A 100 cm 3 styrofoam cup with a lid  50 m l measuring cylinder (a) Write a balanced equation (including state symbols) for the reaction between solid Mg(OH)2 and hydrochloric acid. [1] ………………………………………………………………………………………………. (b) Given that the enthalpy change of reaction between solid Mg(OH) 2 and hydrochloric acid is approximately – 30.0 kJ mol1, prove with calculations whether 50.0 cm3 of 2.5 mol dm–3 HCl and 1.50 g of Mg(OH)2 are suitable quantities to use at the start of the experiment. Justify your answer. [Assuming the specific heat capacity of the solution is 4.2 J g -1 K-1] [4] 805

[Turn over 3 (c) Hence give a detailed procedure to determine the enthalpy change of reaction between solid Mg(OH)2 and HCl. [4] For Examiner’s Use ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. 806

4 (d) Both Group I and Group II hydroxides are white solids. A student accidentally mixes up two unlabelled bottles of white solids, known to contain either KOH or Ba(OH)2. Briefly describe an experiment in which the student can perform in order to determine the identity of the white solids. You are provided with two unknown colourless solutions both at the same concentration of 1.00 mol dm -3, either containing KOH (aq) or Ba(OH) 2 (aq) and FA1: 2.50 mol dm-3 of HCl. [3] For Examiner’s Use ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. [Total: 12] 807

[Turn over 5 2 The graph shows the logarithm, lg, of the ionization energies for the outermost electrons of element X in Period 4. For Examiner’s Use (a) From the graph above, deduce the group in the Periodic Table to which X is likely to belong to and explain your reasoning. Hence, suggest an identity for element X. [2] …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. Identity of X: ………………………………………………………………………………….. 0 5 10 15 Number of electrons removed 0 1 2 3 4 5 lg I.E. 808

6 (b) (i) Sketch a graph for elements of the third period (sodium to chlorine) to show how each property changes across the period. I. Atomic and Ionic Radius ( on the same graph) II. Melting Point Explain your sketches. For Examiner’s Use …………………………………………………………………………………………. ………………………………………………………………………………………… …………………………………………………………………………………………. ………………………………………………………………………………………… …………………………………………………………………………………………. ………………………………………………………………………………………… …………………………………………………………………………………………. ………………………………………………………………………………………… …………………………………………………………………………………………. ………………………………………………………………………………………… 809

[Turn over 7 For Examiner’s Use ………………………………………………………………………………………… …………………………………………………………………………………………. ………………………………………………………………………………………… …………………………………………………………………………………………. ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………………. ………………………………………………………………………………………… …………………………………………………………………………………………. ………………………………………………………………………………………… 810

8 (ii) State and explain the trend of atomic radius of transition metals across the period from titanium to copper. [8] For Examiner’s Use ………………………………………………………………………………………… …………………………………………………………………………………………. ………………………………………………………………………………………… [Total: 10] 3 Explain the following observations as fully as you can. Write equations where appropriate. (a) (i) When NH 3(aq) is added to a solution containing Cu 2+(aq), a light blue precipitate which is soluble in an excess of NH 3(aq) to form a dark blue solution is formed. ………………………………………………………………………………………….. ………………………………………………………………………………………….. ………………………………………………………………………………………….. ………………………………………………………………………………………….. (ii) When concentrated hydrochloric acid is added to another solution containing Cu2+(aq), there is a colour change from blue to pale yellowish-green. No such colour change occurs when concentrated sulfuric acid is added to Cu2+(aq). [4] ………………………………………………………………………………………….. ………………………………………………………………………………………….. ………………………………………………………………………………………….. ………………………………………………………………………………………….. 811

[Turn over 9 (b) 3-bromo-3-methylhexane, CH 3CH2C(Br)(CH3)CH2CH2CH3, reacts with ethanolic sodium cyanide to form a mixture that does not rotate light. [2] For Exa