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

$0.833 \, \text{mol}$ of a hydrocarbon contains $10 \, \text{g}$ of hydrogen. If the empirical formula of the compound is $CH_2O$,determine its molecular formula.

$0.5 \ g$ of hydrocarbon gave $0.9 \ g$ of water on combustion. The percentage of carbon in the hydrocarbon is:

What is the mass percent of oxygen in ethanol $(C_2H_5OH)$ (in $\%$)?

An organic compound having molecular mass $60$ is found to contain $C = 20\%$,$H = 6.67\%$,and $N = 46.67\%$,while the rest is oxygen. On heating,it gives $NH_3$ along with a solid residue. The solid residue gives a violet color with alkaline copper sulphate solution. The compound is:

An organic compound contains carbon,hydrogen,and oxygen. Its elemental analysis gives $38.71 \%$ of $C$ and $9.67 \%$ of $H$. The empirical formula of the compound would be $:-$