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] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (b) (i) The theoretical value for the concentration of hydrogen peroxide is 0.130 mol dm −3. Calculate the percentage error, giving your answer to one decimal place. [1] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (ii) Outline a reason which may explain the difference between the theoretical and experimental values, and suggest an improvement. [2] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………….

− 4 − Turn over 2. The frequencies, f, of the first six lines of the hydro gen emission spectrum which result from electronic transitions to the lowest energy level in the atom are given in the first column in the table below. The differences ∆f between successive frequencies are given in the right hand column. f / 1014 s−1 ∆f 24.66 4.57 29.23 1.60 30.83 0.74 31.57 0.40 31.97 0.24 32.21 0.16 32.37 The graph of ∆f (vertical axis) against f (horizontal axis) is plotted below. (a) Using the linear fit for data set, calculate a value for the frequency when ∆f is zero. [1] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (This question continues on the following page) 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 24.00 25.00 26.00 27.00 28.00 29.00 30.00 31.00 32.00 33.00 Δf f / 1014 s−1 Linear fit for data set y = (−0.5897 × 10−14)x + 19.022

− 5 − Turn over (Question 2 continued) (b) The frequency calculated when ∆f is zero can be used to determine the ionisation energy of hydrogen using the following two steps. Step 1: Energy emitted due to the energy change in an atom can be calculated using ∆E = hf where h is 6.63 × 10−34 J s. Step 2: The energy emitted by 1 mole of atoms can be calculated using E = (∆E)(L) where L is the Avogadro’s constant. Using the frequency calculated in part (b) and the two steps, calculate the ionisation energy of hydrogen. [2] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………….

− 6 − Turn over 3. A student is assigned the task of determining the number of moles of water in one mole of MgCl2·nH2O. The student collects the data shown in the following table. Mass of empty container 22.347 g Initial mass of sample and container 25.825 g Mass of sample and container after first heating 23.982 g Mass of sample and container after second heating 23.977 g Mass of sample and container after third heating 23.977 g (a) Explain why the student can correct ly conclude that the hydrate was heated a sufficient number of times in the experiment. [1] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (b) Determine the value of n. [3] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (c) Another student heats the hydrate in an uncovered crucible, and some of the solid spatters out of the crucible. State and explain the effect it has on the value of n. [2] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………….

− 7 − Turn over Section B Answer all of the questions. Write your answers in the boxes provided. Option D – Medicinal chemistry 4. Ganiclovir and foscarnet are antiviral medications. Ganiclovir is used to treat or prevent infection by cytomegalovirus infections. It prevents replication of viral DNA. One of its side effects is anemia, a condition that develops when blood lacks healthy red blood cells. Ganciclovir and foscarnet show synergistic inhibition of cytomegalovirus. Ganciclovir (a) Identify four functional groups in Ganiclovir. [2] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (b) Many drugs are taken orally. State two other methods of medicinal drugs administration and identify which method has the more rapid effect. [2] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (Option D continues on the following page)

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