Empirical and Molecular Formula

Calculate the molecular formula of compound which contains $20\% \mathrm{Ca}$ and $80\% \mathrm{Br}$ (by weight), if molecular weight of compound is $200$. (atomic weight of $\mathrm{Ca}=40, \mathrm{Br}=80$)

The molecular weight of a compound is $180.$ If its empirical formula is ${\mathrm{CH}}_2\mathrm{O}$ then the molecular formula of the compound is?

$64 \mathrm{g}$ of an organic compound has $24 \mathrm{g}$ of carbon and $8 \mathrm{g}$ of hydrogen and the rest is oxygen. The empirical formula of the compound is

$14 \mathrm{g}$ of an element $\mathrm{X}$ combines with $16 \mathrm{g}$ of oxygen. The element $\mathrm{X}$ could have an atomic weight of

$5 \mathrm{moles}$of ${\mathrm{H}}_2{\mathrm{SO}}_4$ contain:

The empirical formula of a substance whose composition includes $\mathrm{H},\mathrm{C},\mathrm{O}$ and $\mathrm{N}$ in the mass ratio$1: 3: 4: 7$ is:

One volume of a gaseous organic compound of $\mathrm{C}, \mathrm{H}$ and $\mathrm{N}$ on combustion produced $2$ volumes of ${\mathrm{CO}}_2, 3.5$ volumes of ${\mathrm{H}}_2\mathrm{O}$ vapour and $0.5$ volume of ${\mathrm{N}}_2$ under identical conditions of temperature and pressure. The molecular formula of the compound is

$1 \mathrm{mol}$ of a compound contains $1 \mathrm{mol}$ of $\mathrm{C}$ and $2 \mathrm{mol}$ of $\mathrm{O}$. The molar mass of the compound is

For ${\mathrm{CuSO}}_4·5{\mathrm{H}}_2\mathrm{O},$ which is the correct mole relationship?

What is the ratio of the number of oxygen atoms in ${\mathrm{Ca}}_3({\mathrm{PO}}_4{)}_2$ and ${\mathrm{H}}_3{\mathrm{PO}}_3$, if both contain the same number of $\mathrm{P}$ atoms?

How many moles of magnesium phosphate ${\mathrm{Mg}}_3({\mathrm{PO}}_4{)}_2$ will contain $0.25$ mole of oxygen atoms?

The amount of phosphorus present in $1.375 \mathrm{g}$ of ${\mathrm{PCl}}_3$ is

(Atomic weight of $\mathrm{P}=31$, $\mathrm{Cl}=35.5$)