SRJC_H2_CHEM_P2_QP

1 SRJC 9647/02/PRELIM/2014 Turn Over] SERANGOON JUNIOR COLLEGE General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CLASS CHEMISTRY 9647/02 Preliminary Examination 22 August 2014 Paper 2 Structured Questions (SPA) 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet. 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 work. Answer all questions in the space provided. You are advised to spend 30 minutes on question 1. 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 questions. This document consists of 19 printed pages and 1 blank page For Examiner’s Use 1(P) /12 2 /20 3 /13 4 /12 5 /15 TOTAL P2 /72 For Examiner’s Use P1 /40 P2 /72 P3 /80 GRAND TOTAL /192 % GRADE

2 SRJC 9647/02/PRELIM/2014 Turn Over] Answer all questions in the space provided 1 Planning (P) Borax, also known as sodium tetraborate decahydrate, Na 2B4O5(OH)4.10H2O, is a controlled poison in Singapore and cannot be bought off the shelf. Borax dissolves slightly in water to form an alkaline solution: Na2B4O5(OH)4(s) ⇌ 2Na+(aq) + [B4O5(OH)4]2-(aq) [B4O5(OH)4]2-(aq) + 5H2O(l) ⇌ 4H3BO3(aq) + 2OH-(aq) The solubility product of borax at 30°C can be determined via volumetric analysis using hydrochloric acid solution. (a) Assuming that a cm3 of 0.500 mol dm -3 HCl is required for titrati ng 25.0 cm 3 of borax solution at 30°C, calculate the solubility product of borax (excluding units) in terms of a. [3] (b) Deduce the sign for ∆S for the dissolution of borax . Hence, predict whether this process will be more or less feasible at a higher temperature, given that ∆H is endothermic. ……………………………………………………………………….……………….……… …………………………………………………………………………………………..…… ………………………………………………………………………………………..……… …………………………………………………………………………………………..…… [2] For Examiner’s Use

3 SRJC 9647/02/PRELIM/2014 Turn Over] (c) The solubility of borax can also be defined as 30 g of solid that will dissolve in 100 g of w