Which reagent is commonly used in titration to determine the hardness of water?

The amount of oxalic acid in a solution can be determined by titration with $KMnO_4$ in the presence of $H_2SO_4$. If the titration is performed in the presence of $HCl$,the results are unsatisfactory because $HCl$ ...

Why in the redox titration of $KMnO_4$ vs oxalic acid,do we heat the oxalic acid solution before starting the titration?

An aqueous solution of $6.3 \ g$ of oxalic acid dihydrate is made up to $250 \ mL$. The volume of $0.1 \ N \ NaOH$ required to completely neutralise $10 \ mL$ of this solution is.......$mL$

Two acids $A$ and $B$ are titrated separately. $25 \ mL$ of $0.5 \ M \ Na_2CO_3$ solution requires $10 \ mL$ of $A$ and $40 \ mL$ of $B$ for complete neutralization. The volumes (in $L$) of $A$ and $B$ required to produce $1 \ L$ of $1 \ N$ acid solution respectively are:

The strength of an aqueous solution of $I_2$ can be determined by titrating the solution with a standard solution of: