WAEC Chemistry 2025 Theory — Question 63

Question 63 of 70 from the West African Examinations Council (WAEC) Chemistry 2025 Theory paper, with the correct answer and a full explanation.

Alternative A, Q1(b)(ii). Calculate the concentration of solution B in mol/dm3.

Model answer

From the equation, mole ratio NaHCO3 : HCl = 1:1, so nA:nB = 1:1. Using CaVa/CbVb = na/nb: Ca = 0.0904 mol/dm3, Va = 18.30 cm3, Vb = 25.0 cm3, na = nb = 1. Cb = (Ca x Va)/(Vb) = (0.0904 x 18.30)/25 = 0.067 mol dm-3.

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