The sulphate of a metal $M$ contains $9.87\%$ of $M$. This sulphate is isomorphous with $ZnSO_4 \cdot 7H_2O$. The atomic weight of $M$ is (in $.3$)

The empirical formula of a compound is $CH_2O$ and its molecular mass is $90$. The molecular formula of the compound is:

$A$ substance contains $38.8\%$ carbon,$16\%$ hydrogen,and $45.2\%$ nitrogen. What is the empirical formula of this substance?

$A$ transition metal $M$ forms a volatile chloride which has a vapour density of $94.8$. If it contains $74.75\%$ of chlorine,the formula of the metal chloride will be:

An organic compound contains $60\ \%\ C$, $4.48\ \%\ H$, and $35.5\ \%\ O$. Its empirical formula 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 $56 \ u, N_A = 6.022 \times 10^{23} \ mol^{-1}$)