VS 2024 O Level Pure Chemistry P1+P2 Answer Scheme

Victoria School 2024 Chemistry O Levels / 6092 Suggested Answer Key PAPER 1 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 Q19 Q20 B C D D A B A A C B D D C B C B D C D A Q21 Q22 Q23 Q24 Q25 Q26 Q27 Q28 Q29 Q30 Q31 Q32 Q33 Q34 Q35 Q36 Q37 Q38 Q39 Q40 C A B D D B B D D A A A C B A A A B C C PAPER 2 (SECTION A) Question Answer Mark 1 ai A and E 1 aii A and D 1 aiii A and F 1 b colourless; purple 1 c 2C 3 H 6 (g) + 9O 2 (g) → 6CO 2 (g) + 6H 2 O(g) Since 2C 3 H 6 9O 2 ≡ Hence, volume of O 2 gas at r.t.p = x 9 = 450 cm 3 100 2 Volume of air required = x 450 = 2142 cm 3 2140 cm 3 (to 3 sig. fig) 100 21 ≈ 3 2024 Answer 1

2 a Iron, chromium and nickel are elements found in the Periodic Table. They are pure substances that cannot be split up into two or more simpler substances by chemical processes or by electricity . Iron( III ) oxide (Fe 2 O 3 ) is compound that is made up of two or more elements chemically combined in a fixed ratio of iron and oxygen. Steel is a mixture formed when two or more substances are added together without chemical bonds being formed/physically combined . In this steel, the percentage by mass of the 3 constituents, namely iron, nickel and chromium are different with no fixed ratios / proportions. 1 1 1 b To justify this statement, the amounts / number of atoms of the respective metals need to be calculated. Assume 100 g of steel, Amount of Cr = = 0.300 mol 15 . 6 52 Amount of Ni = = 0.151 mol 8 . 9 59 Since the mole ratio of Cr to Ni is approximately 2:1, the statement made by the student is correct. 1 1 c ● The atoms of the different metals should have different sizes/atomic radii but the figure shows particles of the same size . ● There are three different types of atoms in this steel but the figure only shows two different types . ● There are different and varying amounts of constituents in the steel but the ratio of the different particles is almost equal due to the alternate arrangement of the two different constituents shown in the figure. ● The arrangement of particles / atoms in alloys should be disorderly but the figure shows orderly arrangemen t of the particles in steel. (Any three of the above answers are sufficient to score full marks.) 3 2024 Answer 2

d Steel is harder, stronger , less malleable and more brittle than iron. When different elements are added to the pure metal, the atoms of the different elements have different atomic