WAEC Chemistry 2019 Theory — Question 3
Question 3 of 28 from the West African Examinations Council (WAEC) Chemistry 2019 Theory paper, with the correct answer and a full explanation.
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1(c)(i) Explain briefly why calcium oxide cannot be used to dry hydrogen chloride gas. (ii) State one drying agent for hydrogen chloride gas. [3 marks]
Model answer
(i) Calcium oxide is alkaline (basic) while hydrogen chloride gas is acidic, so the two would react together instead of the CaO simply drying the gas. (A drying agent must not react chemically with the gas it is drying.) (ii) Concentrated tetraoxosulphate(VI) acid (concentrated H2SO4) is normally used to dry hydrogen chloride gas.
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