The molecular formula of feldspar is

By usual analysis, $1.00 \ g$ of compound $(X)$ gave $1.79 \ g$ of magnesium pyrophosphate. The percentage of phosphorus in compound $(X)$ is: (nearest integer)
(Given, molar mass in $g \ mol^{-1}$; $O=16, Mg=24, P=31$)

$A$ compound contains $75.8\%$ of $X$ and $24.2\%$ of $Y$ by mass. If the atomic weights of $X$ and $Y$ are $24$ and $16$ respectively,find the empirical formula of the compound.

On complete combustion of $0.492 \text{ g}$ of an organic compound containing $C$, $H$, and $O$, $0.7938 \text{ g}$ of $CO_2$ and $0.4428 \text{ g}$ of $H_2O$ were produced. The percentage composition of oxygen in the compound is $........$

The percentage of oxygen in $NaOH$ is (in $\%$)

When equal weights of the two fertilizers,urea and ammonium sulphate are taken,urea contains