$A$ gaseous compound of nitrogen and hydrogen contains $12.5\%$ (by mass) of hydrogen. The density of the compound relative to hydrogen is $16$. The molecular formula of the compound is

Hemoglobin contains $0.34 \%$ of iron by mass. The number of $Fe$ atoms in $3.3 \ g$ of hemoglobin is. (Given : Atomic mass of $Fe$ is $56 \ u, N_A = 6.022 \times 10^{23} \ mol^{-1}$)

The molecular mass of caffeine is $194 \, a.m.u.$. It contains $28.9 \%$ of nitrogen by mass. The number of nitrogen atoms in one molecule of caffeine is ...............

Chlorophyll, the green pigment in plants responsible for photosynthesis, contains $2.68\%$ of magnesium by mass. Calculate the number of magnesium atoms in $2.00 \ g$ of chlorophyll.

If two compounds have the same empirical formula but different molecular formulas,which of the following do they possess?

An organic compound weighing $500 \ mg$ produced $220 \ mg$ of $CO_2$ on complete combustion. The percentage composition of carbon in the compound is $..........\%$. $(nearest \ integer)$ $(Given \ molar \ mass \ in \ g \ mol^{-1} \ of \ C: 12, O: 16)$