Answer to Question #167922 in Physical Chemistry for Sagar kolte

Question

A water sample was alkaline to both phenolphthalein and methyl orange end point. 50 ml water sample required 20 ml N/50 H2SO4 for P end point and another 5 ml for complete neutralisation Calculate type and amount of alkalinity present.

Answer 1

C(H₂SO4₄) = 0.02 / 2 = 0.01 M

CO₃^2- + H⁺ = HCO₃ ^- (20 ml)

HCO₃^- + H⁺ = H₂O + CO₂ (5 ml)

There is a mistake in a question: the volume untill P point is for the first equotion. It equals to half of amount of CO₃^2-. The second volume (untill M point) is due to another half of CO₃^2- plus all amount of HCO₃. So the second volume can't be bigger than the first one.