54. Solving a chemistry problem

61. a) What substances can be determined iodometrically (by direct titration, substitution method, back titration method)? b) How many grams of HCl is contained in 250 ml of a solution of hydrochloric acid, if 24.00 ml of a 0.0200 N solution of thiosulfate is consumed per 25.00 ml of this solution.