2018 HCIS IB2 HL Prelim Paper 3

− 1 − Turn over PRELIMINARY EXAMINATION International Baccalaureate 2 Chemistry Higher level Paper 3 Wednesday 29 August 2018 (morning) 1 hour 15 minutes Candidate name Candidate session number Class Instructions to candidates • Write your candidate name and session number in the boxes above. • Do not open this examination paper until instructed to do so. • Answer all the questions. • Write your answers in the boxes provided. • A calculator is required for this paper. • A clean copy of the Chemistry data booklet is required for this paper. • The maximum mark for this examination paper is [45 marks]. Section A Questions Answer all questions. 1 − 3 Section B Questions Answer all of the questions from the option. Option D – Medicinal chemistry 4 − 10 For Examiner’s Use Section A / 15 Section B / 30 Total / 45 14 pages © Hwa Chong International School 2018

− 2 − Turn over Section A Answer all questions. Write your answers in the boxes provided. 1. A student submitted the following report on his recent experiment to determine the concentration of a solution of hydrogen peroxide. Method 10 cm3 of hydrogen peroxide was measured using a 100 cm 3 measuring cylinder and placed in a 100 cm3 conical flask. A bung and tubing was attached and the other end connected to a 100 cm 3 gas syringe. Approximately 0.2 g of the MnO 2 catalyst was weighed . The catalyst was added to the hydrogen peroxide solution and the bung quickly replaced. Oxygen gas was collected in a gas syringe and the total volume was recorded. Results Experiment 1 2 3 Mass of MnO2 / g 0.211 0.242 0.202 Volume of gas produced / cm3 15.0 13.0 13.0 Analysis The equation for the reaction: 2H2O2 → 2H2O + O2 Average volume of gas produced = 13.7 cm3 Assuming room temperature and pressure, amount (in moles) of gas = 13.7 cm3 24000 cm3 mol-1 = 5.69 × 10−4 mol 2 mol of H2O2 produce 1 mol of O2, so the amount (in moles) of H2O2 in 10 cm3 = 1.139 × 10−3 mol Concentration of H2O2 = 1.139 × 10−3 mol 0.010 dm3 = 0.114 mol dm−3 (a) The uncertainty of each piece of instrument used is shown below. 100 cm3 measuring cylinder ± 0.5 cm3 100 cm3 gas syringe ± 0.5 cm3 100 cm3 conical flask ± 5 cm3 Weighing balance ± 0.001 g (This question continues on the following page)

− 3 − Turn over (Question 1 continued) (i) Calculate the percentage uncertainty of the concentration of hydrogen peroxide determined by the student. [2] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (ii) Suggest how this percentage uncertainty can be reduced using the same equipment. [1] ………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………….