The molar mass of caffeine is $194$. It contains $28.9\%$ of nitrogen by mass. The number of nitrogen atoms in one molecule of caffeine is:

The percentage composition of an organic compound is as follows: $C = 10.06\%$,$H = 0.84\%$,$Cl = 89.10\%$. Which of the following corresponds to its molecular formula if the vapour density is $60.0$?

The empirical formula of a compound is $CH_{2}O$. $0.0835 \ mol$ of the compound contains $1.0 \ g$ of hydrogen. What is the molecular formula of the compound?

Complete combustion of a hydrocarbon yields $0.72 \ g$ of water and $3.08 \ g$ of $CO_2$. What is the empirical formula of the hydrocarbon?

Quantitative analysis of an organic compound $(X)$ shows the following percentage composition: $C: 14.5\%$,$Cl: 64.46\%$,and $H: 1.8\%$. The empirical formula mass of the compound $(X)$ is $.......... \times 10^{-1}$. (Given molar mass in $g \ mol^{-1}$ of $C: 12, H: 1, O: 16, Cl: 35.5$)

On reduction with hydrogen,$3.6 \ g$ of an oxide of metal $(M)$ left $3.2 \ g$ of the metal. If the atomic weight of the metal is $64$,the formula of the oxide is: