WAEC Chemistry 2010 Theory — Question 45
Question 45 of 46 from the West African Examinations Council (WAEC) Chemistry 2010 Theory paper, with the correct answer and a full explanation.
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8b(ii) Calculate the volume of gas produced at the anode at s.t.p. [1F=96500C, Molar volume of gas at s.t.p=22.4dm³ mol⁻¹]
Model answer
I = 1.25A, t = 40 mins = (40x60)s = 2400s. Q = It = (1.25x2400)C = 3000C. 4OH⁻→2H2O+O2+4e⁻ requires 4 moles of electrons (4Fx96500C) to produce 1 mole of O2 (22.4 dm³ at s.t.p). Hence, 3000C will produce (22.4dm³x3000C)/(4x96500C) = 0.174 dm³ = 174 cm³.
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