WAEC Chemistry 2019 Theory — Question 14
Question 14 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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3(a)(i) In the Solvay process, explain briefly with equations the functions of the following substances: (i) Limestone; (ii) ammonia. [7 marks]
Model answer
• Limestone (CaCO3): its function is to decompose on heating to produce calcium oxide (used to regenerate ammonia from NH4Cl) and carbon(IV) oxide (used in forming the sodium hydrogentrioxocarbonate(IV)): CaCO3 →(Δ)→ CaO + CO2 • Ammonia (NH3): it combines with water and carbon(IV) oxide to form ammonium hydrogentrioxocarbonate(IV), which then reacts with brine to precipitate sodium hydrogentrioxocarbonate(IV): NH3 + H2O + CO2 → NH4HCO3
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