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?

Hemoglobin in red blood cells contains $0.33\%$ iron by mass. The molecular weight of hemoglobin is $67000$. What is the number of iron atoms present in each molecule of hemoglobin? (Atomic mass of $Fe = 56 \ g/mol$)

The value of $n$ in the molecular formula $Be_n Al_2 Si_6 O_{18}$ is

Which of the following substances produces $17.6 \ g$ of $CO_2$ and $7.2 \ g$ of $H_2O$ upon complete combustion with excess oxygen?

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

An organic compound contains $78\%$ (by $wt.$) carbon and the remaining percentage of hydrogen. The correct option for the empirical formula of this compound is: [Atomic $wt.$ of $C$ is $12$,$H$ is $1$]