Fig. 12.1 shows a blast furnace divided into three zones, A, B and C, at different heights. (a) Name the three solid raw materials added at the top of the f...
Question 1 Report
Fig. 12.1 shows a blast furnace divided into three zones, A, B and C, at different heights.
(a) Name the three solid raw materials added at the top of the furnace. [3]
(b) In zone C, coke burns in the hot air. Write the balanced equation and state whether the reaction is exothermic or endothermic. [2]
(c) In zone B, carbon monoxide is formed. Describe how it is formed and write the balanced equation. [2]
(d) In zone A, the ore is reduced. Write the balanced equation for the reduction of Fe2O3 by carbon monoxide. [2]
(e) Explain, in terms of oxygen, why the reaction in part (d) is described as a reduction. [1]
(f) Limestone decomposes in the furnace. Write the equation and name this type of reaction. [2]
(g) The calcium oxide produced reacts with silicon dioxide impurity. Write the equation and name the product formed. [2]
(h) State two ways in which operating a blast furnace can harm the environment. [2]
Answer Details
This question follows the reactions inside a blast furnace zone by zone, testing raw materials, equations, redox, and environmental effects.
(a) The three solid raw materials added at the top are: iron ore (haematite, \( \mathrm{Fe_2O_3} \)) [1]; coke (carbon) [1]; and limestone (calcium carbonate) [1].
(b) In zone C the coke burns in the hot air blasted in:
\[ C + O_2 \rightarrow CO_2 \]This reaction is exothermic [1] (equation [1]), and it supplies the heat that drives the furnace.
(c) In zone B the carbon dioxide rising up the furnace meets more hot coke and is reduced to carbon monoxide [1]:
\[ CO_2 + C \rightarrow 2CO \]The equation scores [1]. Carbon monoxide is the gas that actually reduces the ore.
(d) In zone A the carbon monoxide reduces the iron ore to molten iron:
\[ Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2 \]One mark for formulae, one for balancing [2].
(e) It is a reduction because the iron(III) oxide loses its oxygen [1] to the carbon monoxide.
(f) The limestone decomposes when heated:
\[ CaCO_3 \rightarrow CaO + CO_2 \]This is called thermal decomposition [1] (equation [1]).
(g) The calcium oxide removes the sandy silicon dioxide impurity:
\[ CaO + SiO_2 \rightarrow CaSiO_3 \]The product is calcium silicate, which runs off as molten slag [1] (equation [1]).
(h) Any two environmental harms, one mark each up to [2]: carbon dioxide released causes climate change / global warming; carbon monoxide produced is a toxic gas; sulfur dioxide from impurities causes acid rain; heat and dust pollution; loss of land and habitats through mining the ore.
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