What is the equivalent mass of oxalic acid $(H_2C_2O_4 \cdot 2H_2O)$?

$3.011 \times 10^{22}$ atoms of an element weigh $1.15 \ g$. The atomic mass of the element is: (in $amu$)

At $STP$,if $5.6 \ L$ of a gas weighs $7.5 \ g$,then identify the gas.

The chemical formula for calcium pyrophosphate is $Ca_2P_2O_7$. The formula for ferric pyrophosphate will be

The equivalent weight of potassium permanganate $(KMnO_4)$ in an acidic solution is:

What are the equivalent weights of $H_3PO_4$ in the following reactions respectively?
$H_3PO_4 + OH^{-} \rightarrow H_2PO_4^{-} + H_2O$
$H_3PO_4 + 2OH^{-} \rightarrow HPO_4^{2-} + 2H_2O$
$H_3PO_4 + 3OH^{-} \rightarrow PO_4^{3-} + 3H_2O$