2018 HCIS IB2 HL Chem Prelim P3 (ans)

2018 IB2 HL Chem Prelim P3 – Answers 1 2018 PRELIMINARY EXAMINATION International Baccalaureate 2 Chemistry Higher level Paper 3 1. (a) (i) Relative uncertainty from measuring cylinder = 0.5 10 Relative uncertainty from gas syringe = 0.5 13.7 Total percentage uncertainty = ( 0.5 10 + 0.5 13.7 )(100) = 8.6% [1] [1] (ii) Use a larger volume of hydrogen peroxide to produce a larger volume of gas [1] (b) (i) % error = 0.130−0.114 0.130 (100) = 12.3% [1] (ii) Not all oxygen is collected / Oxygen is lost during the replacement of bung / (OWTTE) Adapt the equipment so that the MnO 2 catalyst can be mixed with H 2O2 in a sealed system to prevent loss/escape of gas. [1] [1] 2. (a) 0 = (−0.5897 × 10−14)x + 19.022 x = 3.226 × 1015 [1] (b) ∆E = (6.63 × 10−34)(3.226 × 1015) = 2.139 × 10−18 J E = (2.139 × 10−18)(6.02 × 1023) = 1.287 × 106 J or 1287 kJ [Answer can be in J or kJ.] [1] [1] 3. (a) The mass remains relatively constant after the second and third heating. / There is no further decrease in mass. [1] (b) mH2O = 25.825 – 23.977 = 1.848 g m2 – m3 nH2O = 1.848 18.02 = 0.1026 mol mMgCl2 = 23.977 – 22.347 = 1.63 g m3 – m1 nMgCl2 = 1.63 24.31+2(35.45) = 0.0171 mol nMgCl2 : nH2O = 0.0171 : 0.1026 = 1 : 6 n = 6 [1] [1] [1] (c) Value of n increases. The mass of sample and container after heating will be smaller than expected, resulting in a greater mass of H2O / OWTTE [1] [1]

2018 IB2 HL Chem Prelim P3 – Answers 2 4. (a) caboxamide / Hydroxyl / Ether / Alkenyl / Amine [Award 1 mark for 2 correct answer. Award 2 marks for 4 correct answers.] [2] (b) Parenteral; Topical / Rectal / Pulmonary More rapid effect : Parenteral [1] [1] (c) When two or more drugs given at the same time have an effect on the body that is greater than the sum of their individual effects. [1] (d) • A virus can multiply very quickly once inside a host cell • Viruses can mutate their DNA and RNA rapidly, • It is difficult to design drugs that target only the virus and do not affect the host cell Make reference to any point. [1] 5. (a) • Overcome the resistance that bacteria has develop to existing antibiotics / prevent methicillin from being destroyed by penicillinase. • Develop resistance to breakdown of methicillin by stomach so it can be administered orally. • To minimize the adverse side effects [1] [1] (b) β-lactam ring of the drugs interfere with the transpeptidase enzymes that bacteria need to make cell walls / interfere with formation of bacterial cell wall / OWTTE; [1] the increased osmotic pressure causes the bacterium to die / the bacterial cells absorb too much water and burst / OWTTE; [1] [1] [1] (c) Makes methicillin less effective / Destroyed bacteria may be replaced by more harmful bacteria / Allows resistant bacteria population to build up [1] 6. (a) Mild analgesics prevent stimul