What is the percentage composition of $C$ in methanoic anhydride?

Hemoglobin contains $0.334 \% \, Fe$ by weight. If the molecular mass of hemoglobin is approximately $67200 \, g/mol$,determine the number of iron atoms in one molecule of hemoglobin. (Atomic mass of $Fe = 56 \, g/mol$)

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

On combustion,$0.210 \ g$ of an organic compound containing $C$,$H$,and $O$ gave $0.127 \ g$ $H_2O$ and $0.307 \ g$ $CO_2$. The percentages of hydrogen and oxygen in the given organic compound respectively are $:$

If $0.0833 \, \text{mol}$ of a carbohydrate contains $1 \, \text{g}$ of hydrogen and its empirical formula is $CH_2O$,what is its molecular formula?

Calculate the percentage composition of the following elements:
$(a)$ Sulphur in $CN_4H_4S$
$(b)$ Carbon in $C_2H_4O_2$
$(c)$ Nitrogen in $CN_2H_2O$
$(d)$ Hydrogen in $C_6H_6$
Given atomic masses: $C = 12, H = 1, O = 16, N = 14, S = 32$.