(a)(i) State two industrial uses of hdrogen.
(ii) Consider the equation below. Mg(HCO\(_3\))\(_{2(aq)}\) \(\to\) MgCO\(_{3(g)}\) + H\(_2\)0\(_{(l)}\) + CO\(_{2(g)}\)
1. State the type of hardness of water being removed as shown by the above equation.
2. Give two disadvantages of hardness of water.
(b)(i) In the extraction of aluminium by electrolysis, graphite electrodes are used. State the disadvantages of using this type of electrode.
(ii) Calcuim oxide reacts with water to form slaked line: I. Write a balanced equation for this reaction; II. State one use of slaked line.
(c)(i) What is meant by saponification?
(ii) List the raw materials needed for the manufacture of soap.
(iii) Name the main by-product obtained from the manufacture of soap.
(d) With the aid of chemical equations explain briefly how iron is extracted in the blast furnace using iron ore, coke and limestone as raw materials at the:
(i) bottom of the furnace; (ii) middle of the furnace (iii) top of the furnace.
(a)(i) Manufacture of ammonia (Haber process); hydrogenation of vegetable oils to make margarine. (Also manufacture of methanol, and use as a fuel.)
(a)(ii) 1. The hardness removed is temporary hardness. 2. Disadvantages of hard water: it wastes soap (forms an insoluble scum) and it forms scale/fur in kettles, boilers and pipes, reducing their efficiency.
(b)(i) The graphite (carbon) anodes react with the oxygen liberated during electrolysis, burning away as CO2, so they are used up and must be replaced frequently (adding to cost).
(b)(ii) I. \[ \text{CaO} + \text{H}_2\text{O} \to \text{Ca(OH)}_2 \] II. Slaked lime is used to neutralize soil acidity (also for making mortar and softening water).
(c)(i) Saponification is the alkaline hydrolysis of fats or oils (esters) by a hot alkali to produce soap and glycerol.
(c)(ii) Raw materials: a fat or oil (animal fat/vegetable oil) and a concentrated alkali (sodium hydroxide).
(c)(iii) The main by-product is glycerol (propane-1,2,3-triol).
(d) Extraction of iron in the blast furnace
- (i) Bottom (hottest zone): coke burns in the blast of hot air, supplying heat, and slag forms:
\( \text{C} + \text{O}_2 \to \text{CO}_2 \); \quad \( \text{CaO} + \text{SiO}_2 \to \text{CaSiO}_3 \) (slag). Molten iron and slag collect here. - (ii) Middle zone: the CO2 is reduced by more coke, and the carbon(II) oxide formed reduces the ore:
\( \text{CO}_2 + \text{C} \to 2\text{CO} \); \quad \( \text{Fe}_2\text{O}_3 + 3\text{CO} \to 2\text{Fe} + 3\text{CO}_2 \). - (iii) Top (coolest zone): the limestone decomposes:
\( \text{CaCO}_3 \to \text{CaO} + \text{CO}_2 \).
(a)(i) Manufacture of ammonia (Haber process); hydrogenation of vegetable oils to make margarine. (Also manufacture of methanol, and use as a fuel.)
(a)(ii) 1. The hardness removed is temporary hardness. 2. Disadvantages of hard water: it wastes soap (forms an insoluble scum) and it forms scale/fur in kettles, boilers and pipes, reducing their efficiency.
(b)(i) The graphite (carbon) anodes react with the oxygen liberated during electrolysis, burning away as CO2, so they are used up and must be replaced frequently (adding to cost).
(b)(ii) I. \[ \text{CaO} + \text{H}_2\text{O} \to \text{Ca(OH)}_2 \] II. Slaked lime is used to neutralize soil acidity (also for making mortar and softening water).
(c)(i) Saponification is the alkaline hydrolysis of fats or oils (esters) by a hot alkali to produce soap and glycerol.
(c)(ii) Raw materials: a fat or oil (animal fat/vegetable oil) and a concentrated alkali (sodium hydroxide).
(c)(iii) The main by-product is glycerol (propane-1,2,3-triol).
(d) Extraction of iron in the blast furnace
- (i) Bottom (hottest zone): coke burns in the blast of hot air, supplying heat, and slag forms:
\( \text{C} + \text{O}_2 \to \text{CO}_2 \); \quad \( \text{CaO} + \text{SiO}_2 \to \text{CaSiO}_3 \) (slag). Molten iron and slag collect here. - (ii) Middle zone: the CO2 is reduced by more coke, and the carbon(II) oxide formed reduces the ore:
\( \text{CO}_2 + \text{C} \to 2\text{CO} \); \quad \( \text{Fe}_2\text{O}_3 + 3\text{CO} \to 2\text{Fe} + 3\text{CO}_2 \). - (iii) Top (coolest zone): the limestone decomposes:
\( \text{CaCO}_3 \to \text{CaO} + \text{CO}_2 \).
