The value of $x$ in $KAl(SO_4)_x \cdot 12 H_2O$ is $.....$

When a crystalline salt $Na_2SO_4 \cdot xH_2O$ is heated,it loses $55.9\%$ of its weight. What is the formula of the crystalline salt?

Calculate the mass percent of calcium,phosphorus,and oxygen in calcium phosphate $Ca_{3}(PO_{4})_{2}$.

When $0.01 \ mol$ of an organic compound containing $60 \%$ carbon was burnt completely,$4.4 \ g$ of $CO_2$ was produced. The molar mass of the compound is $......... \ g \ mol^{-1}$ (Nearest integer).

On complete combustion,$0.492 \ g$ of an organic compound gave $0.792 \ g$ of $CO_2$. The $\%$ of carbon in the organic compound is $..................$ (Nearest integer)

In a compound made of $X$ and $Y$,their masses are equal. If the atomic masses of $X$ and $Y$ are $30$ and $20$ respectively,then the molecular formula of the compound will be ......... (Its molecular mass $= 120$).