What is the atomicity of aluminium phosphate?

Which of the following properties of an element is not variable?

The equivalent weight of $Zn(OH)_2$ in the following reaction is equal to its: $Zn(OH)_2 + HNO_3 \to Zn(OH)(NO_3) + H_2O$

Write the formulae for the following compounds:
$(a)$ Mercury $(II)$ chloride
$(b)$ Nickel $(II)$ sulphate
$(c)$ Tin $(IV)$ oxide
$(d)$ Thallium $(I)$ sulphate
$(e)$ Iron $(III)$ sulphate
$(f)$ Chromium $(III)$ oxide

Calculate the mass of a single atom of hydrogen.

Naturally occurring boron has $20\%\, _5B^{10}$ and $80\%\, _5B^{11}$. The atomic weight of boron is :-