Calculate the formula unit mass of ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$.

Given: atomic mass of $\mathrm{Cu} = 63.5\mathrm{u}, \mathrm{S}=32\mathrm{u} \mathrm{and} \mathrm{O} = 16\mathrm{u}$.

Calculate the formula unit mass of $\mathrm{NaOH}$

Given: atomic masses of $\mathrm{O}=16\mathrm{u}, \mathrm{Na}=23\mathrm{u}.$

A sample of phosphorus weighs $200 \mathrm{g}$. Calculate the following:
a. Number of phosphorus molecules (${\mathrm{P}}_4$)  in the sample.
b. Number of phosphorus atoms in the sample.

(Given : The atomic mass of Phosphorus is $31$)