$A$ compound of carbon,hydrogen,and nitrogen contains three elements in the respective ratio of $9 : 1 : 3.5$ grams. The empirical formula for the compound is

Analysis of a $60 \, g$ compound gives $C = 24 \, g$,$H = 4 \, g$,and $O = 32 \, g$. What is its empirical formula?

One mole of one of the sodium salts listed below,having carbon content close to $14.3 \%$,produces $1 \ mole$ of carbon dioxide upon heating (atomic mass of $Na = 23, H = 1, C = 12, O = 16$). The salt is:

An oxide of iron contains $69.9\%$ iron. Its empirical formula is: (Given: Molar mass of $Fe$ and $O$ are $56$ and $16 \text{ g mol}^{-1}$ respectively.)

An organic compound has been found to possess the empirical formula $CH_2O$ and molecular weight $90$. The molecular formula of it is $(C = 12, H = 1, O = 16)$.

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 ....................