IJC 2016_H2_CHEM_P3_Teachers_copy Prelims

INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION in preparation for General Certificate of Education Advanced Level Higher 2 CHEMISTRY Paper 3 Free Response Candidates answer on separate paper. Additional Materials: Writing Papers Data Booklet Cover Page 9647/03 26 August 2016 2 hours READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen on both sides of the 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. Answer any four questions. Begin each question on a fresh sheet of paper. You are advised to show all working in calculations. You are reminded of the need for good English and clear presentation in your answers. You are reminded of the need for good handwriting. Your final answers should be in 3 significant figures. At the end of the examination, fasten all your work securely together. The number of marks is given in the brackets [ ] at the end of each question or part question. This document consists of 18 printed pages. Innova Junior College [Turn over TEACHER’S COPY

2 PRELIMINARY EXAM  INNOVA 9647/03/2016 [Turn over Answer any four questions. 1 Data concerning the elements of group II of the Periodic Table, at 298K, are given in the table. Further data may be found in the Data Booklet. M refers to elements of group II. 1st and 2nd IE of M / kJ mol-1 ΔHatom of M / kJ mol-1 ΔHhydration of M2+ / kJ mol-1 Eө/ V Ca 1740 178 –1650 –2.87 Sr 1608 164 –1480 –2.89 (a) The electrode reduction potential Eө of Group II elements gives an indication of the ease with which the following reaction occurs: M(s) M2+(aq) + 2e –– reaction 1 The enthalpy change of reaction 1 can be related to the following factors:  first and second ionisation energy of the element  enthalpy change of atomisation and  enthalpy change of hydration of its gaseous ion. (i) Construct an energy cycle relating the factors above, and use the values given above to calculate the enthalpy change of reaction 1 for calcium. [3] Cycle: all correct compounds with state symbols [2] (deduct 1m for omission of state symbols, Enthalpy change of reaction 1 = 178 + 1740 + (-1650) = +268 kJ mol-1 [1] (ii) By quoting appropriate data from Data Booklet, explain the difference in enthalpy change of hydration of calcium and strontium ions. [2] Ca2+ (0.099nm) has smaller ionic radius than Sr2+(0.113nm) -[1] Since they have the same charge, the charge density of Ca2+ is larger, Thus Ca2+ forms stronger ion-dipole interactions with water molecules [1] ΔHhydration of Ca2+ is more exotherm