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 ornamental of gold having $75\%$ of gold,it is of .............. carat.

Insulin contains $3.4\%$ sulfur. What is the minimum molecular weight of insulin?

If a compound on analysis was found to contain $C = 18.5\%$,$H = 1.55\%$,$Cl = 55.04\%$,and $O = 24.81\%$,then its empirical formula is:

$0.5 \ g$ of an organic compound on combustion gave $1.46 \ g$ of $CO_2$ and $0.9 \ g$ of $H_2O$. The percentage of carbon in the compound is $...........$ ($NEAREST$ $INTEGER$). [$GIVEN$: Molar mass in $g \ mol^{-1}$: $C: 12, H: 1, O: 16$]

Calculate the mass percent of different elements present in sodium sulphate $(Na_{2}SO_{4})$.