AJC_H2_CHEM_P3

AJC JC2 PRELIM 2014 9647/03/H2 [Turn over  ANDERSON JUNIOR COLLEGE 2014 JC2 PRELIMINARY EXAMINATIONS   CHEMISTRY 9647/03 Higher 2 16 September 2014 Paper 3 Free Response 2 hours Candidates answer on separate paper. Additional Materials: Data Booklet Writing paper READ THESE INSTRUCTIONS FIRST Write your name, PDG and register number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer any four questions. Start each question on a fresh sheet of paper. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. 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. At the end of the examination, fasten all your work securely together. This document consists of 12 printed pages.

2 AJC JC2 PRELIM 2014 9647/03/H2 [Turn over  1 (a) An alloy containing only aluminium and magnesium was used in boat–building. A 1.75 g sample of the alloy was dissolved in excess hydrochloric acid. The solution was then made alkaline by the addition of aqueous sodium hydroxide until no further reaction occurred. The resultant mixture was filtered to obtain residue C and filtrate D. Carbon dioxide was passed into D and a white solid E, which contained aluminium, was obtained. Heating E to constant mass gave water vapour and a residue F. F can dissolve in both acid and alkali. (i) Suggest the identity of C, D, E and F. (ii) What type of reaction occurs when E is formed from D? (iii) Residue C obtained above was found to have a mass of 0.18 g. Determine the percentage composition by mass of magnesium in the alloy. [6] (b) Aluminium and beryllium exhibit similar pr operties due to their similarities in electronegativities. Be B A l electronegativity value 1.5 2.0 1.5 (i) Beryllium chloride, BeC l2, has properties similar to those of aluminium chloride, A lCl3. Write a balanced equation to show the reaction of beryllium chloride with limited amount of water. When equimolar amounts of aluminium chloride and ammonia are mixed, compound G is formed. (ii) Explain why these two molecules form compound G. (iii) Draw a dot–and–cross diagram to show the bonding in a molecule of compound G. (iv) Suggest the structural formula of a similar product formed when beryllium chloride reacts with ammonia. [4]

3 AJC JC2 PRELIM 2014 9647/03/H2 [Turn over  (c) Aluminium chloride is used as a catalyst in electrophilic substitution reactions. The chlorination of benzene is represented by the following overall equation. + Cl2 AlCl3 Cl + HCl The reaction occurs in several steps.  The f