The diagram shows part of an iron-making furnace at a coastal steelworks. Iron oxide, coke and limestone enter at the top. Hot air enters near the base. Cok...
Question 1 Report
The diagram shows part of an iron-making furnace at a coastal steelworks. Iron oxide, coke and limestone enter at the top. Hot air enters near the base. Coke burns to provide the high temperature needed in the furnace, and carbon monoxide then reacts with iron(III) oxide to make iron. Limestone also undergoes thermal decomposition to form calcium oxide. The reactions have different energy changes, so the engineer monitors the amount of fuel used and the temperature of the furnace carefully. Molten iron is removed at the bottom.
(a) Name the fuel used in the furnace. [1]
(b) State the element in iron(III) oxide that is removed to make iron. [1]
(c) Complete the balanced equation for reduction of iron(III) oxide.
Fe2O3 + 3CO → 2Fe + ________ [1]
(d) Give the word equation for the complete combustion of carbon. [2]
(e) State whether combustion of carbon is exothermic or endothermic. [1]
(f) Explain how combustion of coke helps the thermal decomposition of limestone. [3]
(g) Give the formula of calcium oxide. [1]
(h) Explain why the molten iron is collected at the bottom of the furnace. [2]
(i) Give two ways in which heat energy is lost from a furnace to its surroundings. [2]
(j) State one reason why controlling the furnace temperature is important. [1]
Answer Details
(a) The fuel is coke, which is mainly carbon. [1]
(b) Oxygen is removed from iron(III) oxide to make iron. [1]
(c) \[\mathrm{Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2}\] The missing product is \(\mathrm{3CO_2}\). [1]
(d) The word equation is carbon + oxygen \(\rightarrow\) carbon dioxide. [2]
(e) Combustion of carbon is exothermic, because it releases heat. [1]
(f) Coke combustion releases heat energy. This raises and maintains the high furnace temperature, providing energy for the endothermic thermal decomposition of limestone. [3]
(g) Calcium oxide has formula \(\mathrm{CaO}\). [1]
(h) Molten iron is dense, so it sinks below the other molten materials, including slag, and collects at the bottom. [2]
(i) Two ways heat is lost are by radiation and by conduction through the furnace walls. Convection to air and hot gases leaving the furnace are also acceptable. [2]
(j) The temperature must be high enough for the required reactions to occur and for iron to melt. Controlling it also avoids wasting fuel by overheating. [1]
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