WAEC Chemistry 2025 Theory — Question 61
Question 61 of 70 from the West African Examinations Council (WAEC) Chemistry 2025 Theory paper, with the correct answer and a full explanation.
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Alternative A, Q1. A was prepared by dissolving 0.82g of HCl in 250cm3 of water. B contains 4.0g of impure NaHCO3 per 250cm3 of solution. Describe the titration and give the equation of reaction.
Model answer
The equation of reaction is: NaHCO3(aq) + HCl(aq) -> NaCl(aq) + CO2(g) + H2O(l). A is put in the burette and titrated against 20.0 cm3 or 25 cm3 portions of B using methyl orange as indicator; average titre (volume of A used) = 18.30 cm3, from rough and 1st/2nd titre readings of 18.20 and 18.40 cm3.
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