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 stimulation of nerve endings at the site of pain by preventing production of prostaglandins. Strong analgesics (temporary) bind to opioid receptors in the brain, preventing transmission of pain impulses in the brain. [1] [1] (b) (i) Phenol and Alcohol [1] (ii) Condensation / Addition−elimination [1] (c) (i) The dose that is lethal to 50% of the population Used in animal trials [1] [1] (ii) Heroin [1]

2018 IB2 HL Chem Prelim P3 – Answers 3 7. (a) Rantidine : compete with histamine for binding at H2 receptors, prevents chain events for production of acid. Omeprazole : proton pump inhibitors, prevent release of acid from parietal cells into stomach. [1] [1] (b) nCH3COONa = 4.28 2(12.01)+3(1.01)+2(16.00)+22.99 = 0.05217 mol [CH3COONa] = 0.05217 0.250 = 0.2087 mol dm−3 pH = 4.76 + log 0.2087 0.50 = 4.38 [1] [1] 8. (a) Ac89 225 → 3 𝛼2 4 + Bi83 213 [1] (b) Monoclonal antibodies can be labelled with an α−emitting radioisotope. The antibodies travel through the body and attach to the cancer cells. Decay of the radioisotope produces α−particles which destroys cancerous cell. [1] [1] 9. (a) [1] (b) Chiral auxillary is one enantiomer of an optically active substance that is temporarily incorporated into a non−chiral molecule to synthesise the desired enantiomer. The auxillary can be removed and recycled after the new product is formed. [1] [1] 10. Anabolic steroids and their metabolites can be extracted and concentrated for detection in low concentrations. Anabolic steroids produces a characteristic mass spectrum which can be compared with a library of known compounds. [1] [1] * *