The equivalent weight of $H_3PO_4$ in the reaction $Ca(OH)_2 + H_3PO_4 \rightarrow CaHPO_4 + 2H_2O$ is

When an ion absorbs $6 \times 10^{20}$ electrons,it gets reduced. What is the number of gram equivalents of the ion?

The heaviest atom amongst the following is

$1 \ amu$ is equal to

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

Naturally occurring boron consists of two isotopes with atomic masses $10.01 \ (I)$ and $11.01 \ (II)$. The average atomic mass of natural boron is $10.81$. Find the percentage abundance of isotopes $(I)$ and $(II)$ respectively.