Mayflower Prelim Ans

Prelim 4Ex Chem 2024 – mark scheme P1 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 B B D D A A C B B C Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 Q19 Q20 D D D C D B B D B D Q21 Q22 Q23 Q24 Q25 Q26 Q27 Q28 Q29 Q30 C B A D C C C D C A Q31 Q32 Q33 Q34 Q35 Q36 Q37 Q38 Q39 Q40 B A D C B A C B B D P2 Section A Suggested answers marks Remarks 1 (a) N [1] (b) He/ Ne/ Ar/ Kr [1] (c) O [1] (d) F/Cl/Br [1] (e) Br/Kr [1] (f) N [1] 2 (a) The lower the relative mass, the shorter the time for diffusion of 100cm3 of the gas. Example: Chlorine, having a higher relative mass of 71, than carbon monoxide, which has a lower relative mass of 28, has a longer diffusion time. [1] [1] (b) 132s [1] (c) Ammonia is very soluble in water and will dissolve in water. [1]

3 (a) (b) (c) (d) pink 0.5 1.25 It has a high pH of 14, therefore It is a strong alkali as this indicates a high concentration of hydroxide ions. Blue Pink [1] [1] [1] [1] [1] 4 (a)(i) CuO H2SO4 [1] [1] (ii) Filtration [1] (iii) sodium metal will be too explosive in oxygen to be heated up in hot air to form sodium oxide. In addition, sodium oxide is soluble in water and will not be filtered off in step 3. [1] [1] (b) It can reduce acidity in soils. [1] (e) [2] 5 (a) A simple molecular structure consists of small discrete molecules held together by weak intermolecular forces of attraction. A giant molecular structure consist of atoms joined together by strong covalent bonds throughout the structure. [1] [1] (b) Diamond consists of carbon atoms covalently bonded throughout its giant molecular structure. a large amount of energy/force to is needed to break the strong bonds. Hence diamond is very hard. [1] [1] (c) graphite is made up of flat hexagonal layers of carbon held together by weak intermolecular forces of attraction. the layers of carbon can easily slide over one another when a force is applied. hence graphite is used as a lubricant. [1] [1] (d) Very high melting and boiling points Does not conduct electricity [1] [1]

6 (a) experiment 1 anode: 4OH-(aq) → 2H2O(l) + O2(g) + 4e- cathode: Ag+(aq) + e- → Ag(s) experiment 2 anode: Ag(s) → Ag+(aq) + e- cathode: Ag+(aq) + e- → Ag(s) [1] [1] [1] For both cathode (b)(i) (ii) A white precipitate is observed as silver chloride is insoluble in water Ag+(aq) + Cl-(aq) → AgCl(s) Silver ions in experiment 1 has all be reduced/discharged to form silver metal while in experiment 2, the silver anode oxidises to form silver ions which increases the supply of silver ions in the solution compared to experiment 1 A white precipitate of silver chloride would be observed in experiment 2 only when sodium chloride is added to test for silver ions. [1] [1] [1] [1] [1] (c) Iron is more react