2017 HCI H1 Chemistry Prelims P2 Questions

This document consists of 11 printed pages (including this cover page) HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 1 CANDIDATE NAME CT GROUP 16S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 2 Candidates answer Section A on the Question Paper. Additional Materials: Answer paper Data Booklet Graph paper (2 sheets) 8872/02 11 September 2017 2 hours READ THESE INSTRUCTIONS FIRST Write your Centre number, index number and name on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue, correction fluid or tapes. The use of an approved scientific calculator is expected, where appropriate. Section A Answer all the questions. Section B Answer two questions on separate answer paper. 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 EXAMINERS’ USE ONLY TOTAL Multiple Choice Section A (Structured) Section B (Free Response) Q1 / 20 Q4 / 20 Q2 / 10 Q5 / 20 Q3 / 10 Q6 / 20 / 30 Subtotal / 40 Subtotal / 40 110

2 2017 HCI Preliminary Examination H1 Chemistry Paper 2 Section A Answer all the questions in this section in the spaces provided. 1 (a) Nitrogen and hydrogen react together to form ammonia in the Haber process. N2(g) + 3H2(g) ⇌ 2NH3(g) H = – 92 kJ mol–1 Industrially, the following conditions are used for the Haber process. pressure 250 atm temperature 450 ˚C catalyst finely divided iron catalyst (i) With the aid of Le Chatelier’s Principle, explain why a moderate temperature of 450 oC is used for the Haber process. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [2] (ii) Explain how iron catalyst can increase the rate of formation of ammonia. ……………………………………………………………………………………………. ………………………………………………………………………………………… [1] (iii) State and e xplain the effect of using a pressure of 400 atm on the position of equilibrium and the equilibrium constant. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [2]

3 2017 HCI Preliminary Examination H1 Chemistry Paper 2 Given that 4 moles of N2 and 8 moles of H2 are allowed to reach dynamic equilibrium in a 2 dm3 vessel. It is found that the total number of moles of gases present in the vessel at equilibrium is 8. (iv) Write a Kc expression for the equilibrium in the formation of ammonia. [1] (v) Calculate the number of moles of each gas at equilibrium, s