An organic compound gave $C = 92.31\%$ and $H = 7.69\%$. If the molecular weight of the compound is $78$,its molecular formula is

Find the empirical formula of the compound if $M = 68 \%$ (Atomic mass $= 34$) and the remaining $32 \%$ is oxygen:

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

The ratio of the mass percentages of $C$ and $H$ and $C$ and $O$ of a saturated acyclic organic compound $X$ are $4 : 1$ and $3 : 4$ respectively. Then,the moles of oxygen gas required for complete combustion of two moles of organic compound $X$ is

$64 \, g$ of an organic compound contains $24 \, g$ of carbon,$8 \, g$ of hydrogen,and the rest oxygen. The empirical formula of the compound is

Calculate the molecular formula of an iron oxide,in which the mass percentages of iron and oxygen are $69.9$ and $30.1$,respectively.