2021_RVHS_Prelim_P2_Ans

River Valley High School 8873/02 [Turn over 2021 JC 2 Preliminary Examination Paper 2 RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME Suggested Answer CLASS 2 0 J INDEX NUMBER H1 CHEMISTRY 8873/02 Paper 2 Structured Questions 15 Sep 2021 2 hours Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST. DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO. Write your name, class and index number in the spaces at the top of this page. Write in dark blue or black pen. You may use an pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions in the space provided. Section B Answer one question in the space provided. A Data Booklet is provided. Do NOT write anything on it. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Paper 1 30 Paper 2 1 9 2 7 3 6 4 5 5 18 6 15 7 20 8 20 s.f. units Paper 2 80 Total 110 This paper consists of 20 printed pages.

2 River Valley High School 8873/02 2021 JC 2 Preliminary Examination Paper 2 Section A (60 marks) Answer all the questions in this section. 1 (a) (i) Describe the reactions, if any, of the chlorides MgC l2 and PCl5 with water. Write equations for all reactions that occur, and suggest the pH of the resulting solutions. Relate the reactivity of the se chlorides to their structure and bonding. ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… [3] MgCl2 has a giant ionic lattice structure and strong electrostatic attraction between Mg 2+ and C l ions. MgC l2 dissolves in water readily to form an acidic solution of pH 6.5. Both hydration of ions and partial hydrolysis of Mg 2+(aq) occurs. Hydrolysis occurs due to the polarisation of water molecules by the Mg2+ ion MgCl2(s) + 6H2O(l)  [Mg(H2O)6]2+(aq) + 2Cl(aq) [Mg(H2O)6]2+(aq) + H2O(l)  [Mg(H2O)5OH]2+(aq) + H3O+(aq) PCl5 has a simple covalent structure. PCl5 dissolves and undergoes hydrolysis in water to form an acidic solution of pH 2. P atom in PCl5 has energetically accessible vacant 3d orbitals to form dative bonds with water molecules. PCl5(s) + 4H2O(l)  H3PO4(aq) + 5HCl(aq) (ii) Carbon is in the same group as silicon. Suggest and explain if CC l4 will react with water.

3 River Valley High School 8873/02 [Turn over 2021 JC 2 Preliminary Examination Paper 2 ……………………………………………………………………………… ……………………………………………………………………………… [1] CCl4 does not react with water as carbon does not ha