2023 XMS P2 PRELIM MS

1 SEC 4E CHEMISTRY 6092 PRELIM 2023 PAPER 2 MARK SCHEME SECTION A (50 marks) A1 (a) (i) O / S / Se 1 (ii) Cl 1 (iii) He 1 (iv) N 1 (v) C 1 (b) (i) Xe O F moles (1) 0.549/131 = 0.00419 0.134/16 = 0.008375 0.317/19 = 0.0167 simplest ratio 1 2 4 XeO2F4 (1) 2 (ii) Relative molecular mass Mr / relative formula mass / molar mass 1 (c) ALLOW same symbol for both atoms correct shared electron pairs (1) rest of molecule correct (1) 2 (d) any one from: physical property oxide of aluminium has a high melting/boiling point but oxide of sulfur has a low melting/boiling point oxide of aluminium conducts electricity when melted but oxide of sulfur does not conduct in any state oxide of aluminium is insoluble in water but oxide of sulfur is soluble in water any one from: chemical property oxide of aluminium is amphoteric but oxide of sulfur is acidic ALLOW oxide of amphoteric but oxide of sulfur is not oxide of aluminium can react with acids and alkalis but oxide of sulfur can only react with alkalis ALLOW oxide of aluminium is ionic but oxide of sulfur is covalent 2 Total 12 A2 (a) (i) Ar of Fe (56) is smaller than Ar of Zn (65) (1) Hence there are more moles in 1.5 g of Fe than Zn(1) 2 (ii) metal that gives a steeper slope / larger gradient / more gas produced per unit time / shorter reaction time for a fixed volume of gas (1) 1 (iii) Any three from: For iron, green precipitate formed (1), insoluble in excess (1) For zinc, white precipitate formed (1), soluble in excess (1) / giving colourless solution 3 (b) (i) Cu2+(aq) + 2e- → Cu(s) balanced eqn (1) state symbols (1) 2 (ii) The concentration decreases 1 (iii) There is no change in the concentration 1 Total 10 O O

2 A3 (a) (i) addition polymerisation (NOT: additional polymerisation) 1 (ii) 1 (iii) Percentage by mass of carbon = %100111 512  (1) = 54.1% (1) 2 (b) (i) 25±1 oC 1 (ii) As the temperature increases, the number of monomer particles having activation energy increases (1) As the particles have more energy, (ACCEPT: move faster) (1) Hence the number of effective collisions (per unit time) increases (1) 3 (iii) 1 Total 9 50 10 20 30 40 0 60 70 5 10 15 20 25 30 0 35 setting time / minutes temperature / oC higher concentration H C N C H C C CH3 O O

3 A4 (a) (i) What are the positions of the four metals in the reactivity series? 1 (ii) D 1 (iii) Ionic equation of this form: X + Y2+ → X2+ + Y e.g. Sn + Cu2+ →Sn2+ + Cu 1 (iv) any of following for (1) copper in copper(II) sulfate tin in tin(II) sulfate iron in iron(II) sulfate zinc in zinc sulfate metal in its own sulfate solution metals in their own sulfate solutions metals do not displace