WAEC Chemistry 2018 Theory — Question 23
Question 23 of 24 from the West African Examinations Council (WAEC) Chemistry 2018 Theory paper, with the correct answer and a full explanation.
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5.(a)(i) State one industrial use of hydrogen gas. (ii) Consider the equation: Mg(HCO₃)₂(aq) → MgCO₃(s) + H₂O(l) + CO₂(g). State the type of hardness of water being removed as shown above. (iii) Give two disadvantages of hardness of water.
Model answer
(i) Hydrogen is used in the manufacture of ammonia (Haber process); it is also used in filling balloons and in the production of methanol. (ii) Since the water contains HCO₃⁻ (bicarbonate) ions, the hardness being removed is temporary hardness. (iii) Disadvantages of hard water: it causes furring of kettles/pipes, and it wastes soap by forming scum before lathering.
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