What is the mass of oxygen in $32.2 \ g$ of $Na_2SO_4 \cdot 10H_2O$ (in $g$)?

The sulphate of a metal $M$ contains $9.87\%$ of $M$. This sulphate is isomorphous with $ZnSO_4 \cdot 7H_2O$. The atomic weight of $M$ is (in $.3$)

$A$ compound containing $Xe$ and $F$ has $63.8\%$ of $Xe$ by mass. Calculate the oxidation number of $Xe$ in this compound.

Which one has the highest percentage of nitrogen?

Two oxides of a metal contain $50\%$ and $40\%$ of the metal,respectively. The formula of the first oxide is $MO$. What is the formula of the second oxide?

On complete combustion,$1.0 \ g$ of an organic compound $(X)$ gave $1.46 \ g$ of $CO_2$ and $0.567 \ g$ of $H_2O$. The empirical formula mass of compound $(X)$ is $.......... \ g \ mol^{-1}$. (Given molar mass in $g \ mol^{-1}: C: 12, H: 1, O: 16$)