WAEC Chemistry 2025 Theory — Question 62

Question 62 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)(i). Calculate the concentration of solution A in mol/dm3.

Model answer

250 cm3 of HCl contains 0.825g (0.82g rounded). 1000 cm3 will contain (1000 x 0.825)/250 = 3.30 g/dm3. Molar mass of HCl = 1 + 35.5 = 36.5 g/mol. Concentration of A in mol/dm3 = 3.30/36.5 = 0.0904 mol dm-3.

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