WAEC Chemistry 2018 Theory — Question 24
Question 24 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.(b)(i) In the extraction of aluminium by electrolysis, graphite electrodes are used. State the disadvantage of using this type of electrode. (ii) Calcium oxide reacts with water to form slaked lime. Write a balanced equation for this reaction, and state one use of slaked lime.
Model answer
(i) The oxygen gas produced at the anode combines, at the high operating temperature, with the graphite electrode to form CO₂; this leads to the graphite anode being gradually worn away (depleted) and needing frequent replacement. (ii) CaO(s) + H₂O(l) → Ca(OH)₂(s). Slaked lime is used to treat acidic soil (and in the manufacture of bleaching powder / mortar).
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