$NaOH + H_3PO_4 \to NaH_2PO_4 + H_2O$; What is the equivalent weight of phosphoric acid in this reaction?

Which of the following is true about sodium chloride?

Chlorine has two isotopes $^{35}Cl$ and $^{37}Cl$ with an average atomic mass of $35.5$. What is the ratio of their relative abundance respectively?

In order to prepare one litre of a $1 \ N$ (normal) solution of $KMnO_4$,how many grams of $KMnO_4$ are required if the solution is to be used in an acidic medium for oxidation?

$209 \ g$ of an element reacts with chlorine to form $315.5 \ g$ of its chloride. What is the weight (in $g$) of oxygen that reacts with $418 \ g$ of same element?
$(Cl = 35.5 \ u; O = 16 \ u)$

If $m_1 \ g$ of metal $A$ displaces $m_2 \ g$ of another metal $B$ from its salt solution,and their equivalent weights are $E_1$ and $E_2$ respectively,how is the equivalent weight of $A$ expressed?