What is the percentage composition of $C$ in methanoic anhydride?

Nickel steel contains $3-5 \%$ of $Ni$. (in $-5 \%$)

In an organic compound,the percentage of $C$ is $92.3 \%$. What is its empirical formula?

The empirical formula of a compound is $CH_2$. If the molar mass of the compound is $42 \ g/mol$,what is its molecular formula?

The complete combustion of $0.492 \, g$ of an organic compound containing $'C'$,$'H'$,and $'O'$ gives $0.793 \, g$ of $CO_{2}$ and $0.442 \, g$ of $H_{2}O$. The percentage of oxygen composition in the organic compound is .... (nearest integer)

$A$ compound has $50\%$ carbon,$50\%$ oxygen and its approximate molecular weight is $290$. Its molecular formula is