2022 Peirce Chemistry Answers

Solutions for 2022 4E Prelim Science Chemistry MCQ 1. A 2. C 3. D 4. C 5. D 6. D 7. A 8. C 9. C 10. B 11. B 12. C 13. A 14. B 15. A 16. C 17. D 18. D 19. B 20. B Section A 1(a) Chromatography [1] 1(b) Any height below the starting line. [1] 1(c) Yes. It contains only permitted dyes. [1] 1(d) To check if athletes consumed banned drugs. or To check the vegetables contained too much pesticides [1] Total 4 Marks 2 A: dilute sulfuric acid / H2SO4 [1] B: barium sulfate/ BaSO4 [1] C: ammonium sulfate / (NH4)2SO4 [1] D: ammonia [1] Total 4 Marks 3(a) D [1] 3(b) F [1] 3(c) C [1] 3(d) B [1] 3(e) C [1] Total 5 Marks

4(a) Number of protons 12 Number of neutrons 25-12 = 13 Number of electrons 12 3 correct 2 mks, less than 3 correct 1mk [2] (bi) Ionic bonding [1] (bii) 1 mk for each ion [2] Total 6 Marks 5(ai) 1+14+3(16) = 63 [1] 5(aii) 126/63 = 2 mol/dm3 [1] 5(b) No. of moles of magnesium carbonate = ½ x 1 = 0.5 mol [1] Total 3 Marks 6(ai) CaCO3 (s) + H2SO4 (aq) → CaSO4 (s) + H2O (l) + CO2 (g) OR CaO (s) + H2SO4 (aq) → CaSO4 (s) + H2O (l) Equation 1 mk S.S 1 mk [2] 6(aii) Filter the mixture and Collect the residue. Rinse with distilled water and Dry between sheets of filter paper. 4 steps 3 mks; 3 steps 2 mks; 2 steps 1mk [3] 6(bi) Substance oxidised: Fe Reason: oxidation state of Fe increases from 0 in Fe to +2 in FeSO4 [1] [1] 6(bii) Substance reduced: H2SO4 Reason: oxidation state of S decreases from +6 in H2SO4 to +4 in SO2 [1] [1] Total 9 Marks

7(a) Bromine / Br2 [1] 7(b) 7 [1] 7(c) X2 [1] 7(d) Any value more than 216 pm [1] 7e(i) LiX [1] 7e(ii) CX4 [1] Total 6 Marks 8(a) X: naphtha Y: kerosene Z: lubricating oil All correct 2 mks; less than 3 correct 1 mk [2] 8(b) C6H14 → C4H10 + C2H4 [1] 8(ci) [1] 8(cii) it produces toxic fumes when burnt. [1] Total 4 Marks 9(a) Test: Bubble butane and butene to aqueous bromine Results: Reddish brown aqueous bromine decolourise by butene rapidly Aqueous bromine remains unchanged by butane Test: 1mk Results: 1mk [1] [1] 9(b) List of substances and conditions: yeast, glucose (solution), Less than 37°C Chemical Equation: C6H12O6→ 2 CH3CH2OH + 2 CO2 [1] [1] Total 4 Marks

Section B 10(ai) 10(b) 10a(i)1 mark for correctly plotted points; 1 mark for curve of best fit 10(b) 1 mark for expt 2 and 3 respectively. [2] and [2] (aii) 6 min [1] (aiii) As the temperature increases, more particles possess energy more than or equal to Ea. OR As temperature increases, particles gain K.E and move faster. This increase the frequency of effective collision and increase the speed of reaction. [1] [1] [1] (c) No. of moles of Zn = 62/65 = 0.9538 mol No. of moles of H2 = 0.9538 mol Volume of gas = 0.9538 x 24 = 22.89 = 22.9 dm3 (3 s.f) [1] [1] Total 10 Marks

11(ai) TiCl4 + 2 Mg→ 2 MgCl2 + Ti [1] 11(aii) magnesium [1] 11(b)