$A$ hydrocarbon contains $75\%$ carbon by mass. What is its empirical formula?

The empirical formula of a compound is $CH_2O$ and its molecular mass is $180$. The molecular formula of this compound is .....

An organic compound containing $C$,$H$,and $N$ gave the following analysis: $C = 40\%$,$H = 13.33\%$,and $N = 46.67\%$. Its empirical formula would be:

In a compound made of $X$ and $Y$,their masses are equal. If the atomic masses of $X$ and $Y$ are $30$ and $20$ respectively,then the molecular formula of the compound will be ......... (Its molecular mass $= 120$).

An alkane has a $C/H$ ratio (by mass) of $5.1428$. Its molecular formula is

Mass percentage of $C, H$ and $O$ in a compound are $60\%$,$13.33\%$ and $26.67\%$ respectively. The molecular weight of the compound is $60$. The molecular formula of the compound is