A quantity of 3 g of impure marble was treated with 200 ml of dil. HCl. After completion of the reaction a small quantity of the residue was left and 560 ml of a gas was evolved at 0°C and 1 atm. The

Question

A quantity of 3 g of impure marble was treated with 200 ml of dil. HCl. After completion of the reaction a small quantity of the residue was left and 560 ml of a gas was evolved at 0°C and 1 atm. The normality of acid solution is

TestHub · Accepted Answer

CO₂ evolved = 560/22400 = 0.025 mol. CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O, so HCl consumed = 2 x 0.025 = 0.05 mol. Residue left means marble is in excess, i.e. the acid is fully consumed, so 200 ml contained 0.05 mol HCl. Normality = 0.05/0.2 = 0.25 N, option (c).

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