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

In nature,carbon exists as a mixture of $C^{12}$ and $C^{13}$. The average atomic mass of carbon is $12.011$. What is the percentage abundance of $C^{12}$ in nature?

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 used in an acidic medium for oxidation?

Statement $1$: The equivalent mass of $Cu$ in $CuO$ is $63.6$ and in $Cu_2O$ is $31.8$. Statement $2$: Equivalent mass = $\frac{\text{Molecular mass}}{\text{Valency}}$

Calculate the milli-equivalents of:
$(a) \, Ca(OH)_2$ in $74 \, g$
$(b) \, NaOH$ in $20 \, g$ respectively.

The equivalent weight of an acid: