2016 HCI H1 Chemistry Prelims P2 Questions

HCI H1 Chemistry Prelim 2016 HWA CHONG INSTITUTION Preliminary Examination Higher 1 CANDIDATE NAME CT GROUP 15S CHEMISTRY Paper 2 Candidates answer Section A on the Question Paper. Additional Materials: Data Booklet Writing paper; Graph paper 8872/02 30 August 2016 2 h READ THESE INSTRUCTIONS FIRST Write your name and CT group 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. Section A Answer all 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 Paper 1 Paper 2 TOTAL Multiple Choice Section A (Structured) Section B (Free Response) Q1 /10 Q4 / 20 Q2 /14 Q5 / 20 Q3 /16 Q6 / 20 / 30 Subtotal / 40 Subtotal / 40 This question booklet consists of 13 printed pages. 110

H1 Chemistry Prelim 2016 2 Section A Answer all the questions in this section in the spaces provided. 1 (a) An equilibrium exists between aqueous chromate (VI) ions and dichromate (VI) ions as shown by the expression below: 2CrO 42-(aq) + 2H+(aq)  Cr2O72-(aq) + H2O(l) Yellow orange (i) State the meaning of the term dynamic equilibrium. ………………………………………………………………………………………. ………………………………………………………………………………………. ……………………………………………………………………………………[1] (ii) Write an expression for the equilibrium constant, K c, for this reaction. [1] (iii) The initial concentration of CrO 42- ions and H+ ions are 0.850 mol dm−3 and 1.20 mol dm−3 respectively. After equilibrium is reached, the concentration of Cr2O72- ions is 0.200 mol dm−3. Calculate the value of K c for this equilibrium and state its units. Kc = ……………………. units = ……………………. [3]

H1 Chemistry Prelim 2016 3 (b) (i) State Le Chatelier’s Principle. ………………………………………………………………………………………. ……………………………………………………………………………………… …………………………………………………………………………………….. …………………………………………………………………………………[1] (ii) Describe and explain what happens to the colour in the beaker when aqueous sodium hydroxide is added. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. ……………………………………………………………………………………[2] (iii) When the beaker