What is the molecular mass of ${\mathrm{BaCl}}_2.2{\mathrm{H}}_2\mathrm{O}$? (At mass of $\mathrm{Cl}=35.5, \mathrm{O}=16, \mathrm{Ba}=137$)

What is the molecular mass of barium sulphate? (At mass of $\mathrm{O}=16, \mathrm{Ba}=137, \mathrm{S}=32$)

What is the molecular mass of aluminium oxide? (At mass of $\mathrm{Al}=27, \mathrm{O}=16$)

A compound on analysis gave the following percentage composition.
$\mathrm{Na}-14.31\%, \mathrm{S}-9.97\%, \mathrm{H}-6.22 \%, \mathrm{O}-69.5\%$. The molecular mass of the substance is $322$. Find its molecular formula assuming that all the hydrogen atoms are present in combination with oxygen as water of crystallisation. (At. mass $\mathrm{Na}=23, \mathrm{H}=1, \mathrm{S}=32, \mathrm{O}=16$)

An organic compound contains $52.18\%$ carbon and $13.04\%$ hydrogen, the remaining being oxygen. The vapour density of the compound is $23$. Calculate the molecular formula.