Calculate the mass of $Ca$ in $g$ present in $Ca(NO_3)_2$ that contains $20 \ g$ of nitrogen.

Empirical formula of a compound is $CH_2O$ and its vapour density is $30$. The molecular formula of the compound is:

Compound $A$ contains $8.7\,\%$ Hydrogen,$74\,\%$ Carbon and $17.3\,\%$ Nitrogen. The molecular formula of the compound is ....
Given : Atomic masses of $C$,$H$ and $N$ are $12$,$1$ and $14\, amu$ respectively.
The molar mass of the compound $A$ is $162\, g\, mol^{-1}$.

An organic compound has the percentage of $C$ and $H$ in the ratio $6 : 1$ and the percentage of $C$ and $O$ in the ratio $3 : 4$. The compound is:

$A$ substance contains $38.8\% \ C$,$16.0\% \ H$,and $45.2\% \ N$. What is the empirical formula of the substance?

$2.0 \text{ g}$ of a bromo hydrocarbon $(X)$ was subjected to Carius analysis, which gave $3.36 \text{ g}$ of $AgBr$. The percentage of carbon in the compound $(X)$ is $26.7\%$. The total number of carbon atoms in the empirical formula for compound $(X)$ is . . . . . . .