2019 SAJC H2 Chem Prelim P2 QP

1 NAME Class ST ANDREW’S JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS Chemistry (9729) Paper 2 Structured Questions 30 August 2019 2 hours Additional Materials: Data Booklet READ THESE INSTRUCTIONS: Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s use: Question 1 2 3 4 5 Total Marks 9 8 20 25 13 75 This document consists of 20 printed pages (including this page).

2 1. (a) P, Q, R and S are consecutive elements in Period 4. The table below shows the first four ionisation energies (in kJ mol–1) of the elements. Element 1st I.E. 2nd I.E. 3rd I.E. 4th I.E. 5th I.E. P 908 1730 3828 5980 7970 Q 577 1980 2960 6190 8284 R 762 1540 3300 4390 9020 S 947 1798 2735 4837 6043 (i) Explain why the second ionisation energy of Q is higher than that of R. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. [2] (ii) Explain why P is not considered to be a transition metal like most of the d-block metals. ………………………………………………………………………………………. ………………………………………………………………………………………. [1] (b) The idea of covalent bonding was first described in 1916 by an American physical chemist Gilbert Newton Lewis. HCOCl is an example of a polar covalent molecule. (i) Explain what is covalent bonding. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. [1]

3 1. (b) (ii) State what is meant by the term polar when applied to a covalent bond. ………………………………………………………………………………………. ………………………………………………………………………………………. [1] (iii) State and explain with reference to the Valence Shell Electron Pair Repulsion theory, the shape of HCOCl molecule. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. [2] (iv) The molecule of HCOCl contains both σ (sigma) and π (pi) bonds. Draw labelled diagrams to show how orbitals overlap to form  a σ (sigma) bond  a π (pi) bond [2] [Total:9]

4 2 Below is a labelled diagram of a hydrogen-oxygen fuel cell in an alkaline electrolyte