Complete combustion of a hydrocarbon yields $0.72 \ g$ of water and $3.08 \ g$ of $CO_2$. What is the empirical formula of the hydrocarbon?

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

Substances $X$ and $Y$ have the same mass. If their atomic weights are $30$ and $20$ respectively,and the molecular weight of the compound is $120$,what is the molecular formula of the compound?

An organic compound on analysis gives the following composition: $C = 54.5\%, O = 36.4\%, H = 9.1\%$. The empirical formula of the compound is ..

The empirical formula of a compound is $C_2H_5O$ and its vapour density is $45$. What is the molecular formula of the compound?

The percentage of $Se$ in peroxidase anhydrous enzyme is $0.5\%$ by weight (atomic weight $= 78.4$). Then,the minimum molecular weight of peroxidase anhydrous enzyme is: