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

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

If the fertilizers listed below are priced according to their nitrogen content,which will be the least expensive per $50 \ kg$ bag?

$A$ compound contains $C = 90\%$ and $H = 10\%$. The empirical formula of the compound is:

$C_4H_6O_2$ does not represent :

$120 \ g$ of an organic compound that contains only carbon and hydrogen gives $330 \ g$ of $CO_{2}$ and $270 \ g$ of water on complete combustion. The percentage of carbon and hydrogen,respectively,are ...... .