$A$ compound contains $2.34 \ g$ of nitrogen and $5.34 \ g$ of oxygen. What is the empirical formula of the compound?

Caffeine has a molecular weight of $194$. If it contains $28.9\%$ by mass of nitrogen,the number of atoms of nitrogen in one molecule of caffeine is:

An organic compound contains $C = 36\%$,$H = 6\%$ and the rest is oxygen. Its empirical formula is:

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

An organic compound is estimated through the Dumas method and is found to evolve $6$ moles of $CO_2$,$4$ moles of $H_2O$,and $1$ mole of nitrogen gas. The formula of the compound is

By combustion of $0.2475 \ g$ of an organic compound,$0.4950 \ g$ of $CO_2$ and $0.2025 \ g$ of $H_2O$ are obtained. Calculate the percentage of $C, H,$ and $O$. Given atomic masses: $C = 12, H = 1, O = 16$.