O-LevelChemistryMetals & Reactivity5070/22 · Oct/Nov 2020 · Q710 Marks

Iron is extracted from iron ore in a blast furnace using limestone and coke (carbon).

(a)Name a common ore of iron.[1]
(b)The coke burns to form carbon dioxide. This reaction is exothermic. Explain, in terms of bond making and bond breaking, why this reaction is exothermic.[2]
(c)(i)Carbon dioxide reacts with hot coke to form carbon monoxide. The carbon monoxide reduces the iron(III) oxide in the iron ore. Fe2O3 + 3CO → 2Fe + 3CO2 Use this equation to explain why the Fe2O3 is reduced.[1]
(c)(ii)Calculate the maximum mass of iron formed when 12.5g of iron(III) oxide react with excess carbon monoxide. mass of iron ................................................ g[2]
(d)Silicon dioxide is an impurity in the iron ore. Explain how the addition of limestone helps remove silicon dioxide from the blast furnace.[2]
(e)Iron is a metal. Describe metallic bonding.[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[1] 7(a) haematite
[1] 7(b) bond breaking endothermic and bond making exothermic/ heat absorbed to break bonds and heat released on making bonds (1)
[1] 7(b) more heat released than absorbed / more energy released than absorbed (1)
[1] 7(c)(i) oxygen removed from iron oxide / it loses oxygen
[1] 7(c)(ii) mol iron oxide = 12.5 / 160 OR 0.078 mol (1)
[1] 7(c)(ii) mass of iron = 8.75g(1)
[1] 7(d) limestone decomposes to calcium oxide / calcium oxide formed from calcium carbonate (1)
[1] 7(d) calcium oxide reacts with silicon dioxide to form slag / calcium oxide reacts with impurities to form calcium silicate (1)
[1] 7(e) idea of metallic structure: (positive) ions and sea of electrons (1)
[1] 7(e) electrostatic attraction between the ions and electrons (1)

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