The empirical formula of a hydrocarbon containing $80\%$ carbon and $20\%$ hydrogen is:

The empirical formula of a compound is $C_2H_5O$ and its molecular weight is $90$. The molecular formula of the compound is:

Determine the empirical formula of an oxide of iron which has $69.9 \%$ iron and $30.1 \%$ dioxygen by mass.

At $STP$,$2.8 \, L$ of a gaseous substance weighs $5.5 \, g$. If the compound contains $N$ and $O$ atoms,its molecular formula will be ..............

An organic compound contains $A$ and $B$ in a mass ratio of $50:50$. If their atomic masses are $10$ and $40$ respectively,then its empirical formula will be ....................

$A$ hydrocarbon contains $10.5 \, g$ of carbon and $1 \, g$ of hydrogen. If the volume of $2.4 \, g$ of this hydrocarbon is $1 \, L$ at $127 \, ^\circ C$ and $1 \, atm$ pressure,then the hydrocarbon is: