An organic compound contains $C = 74.0\%$,$H = 8.65\%$ and $N = 17.3\%$. Its empirical formula is:

Number of $g$ of oxygen in $32.2\,g$ of $Na_2SO_4 \cdot 10H_2O$ is

The simplest formula of a compound containing $50\%$ of element $X$ (at. wt. $= 10$) and $50\%$ of element $Y$ (at. wt. $= 20$) is

$A$ metal oxide $M$ contains $40\%$ oxygen by mass. The atomic mass of metal $M$ is $24$. The empirical formula of the oxide is....

$1.25 \ g$ of a metal $(M)$ reacts with oxygen completely to produce $1.68 \ g$ of metal oxide. The empirical formula of the metal oxide is
[molar mass of $M$ and $O$ are $69.7 \ g \ mol^{-1}$ and $16.0 \ g \ mol^{-1}$,respectively]

$A$ compound has the following composition by weight: $Na = 18.60 \%$,$S = 25.80 \%$,$H = 4.02 \%$,and $O = 51.58 \%$. Assuming that all the hydrogen atoms in the compound are part of water of crystallisation,the correct molecular formula of the compound is: