Calculate the percentage of phosphorus in calcium hydrogen phosphate, ${\mathrm{CaHPO}}_4$.

Calculate the percentage of phosphorus in Calcium phosphate, ${\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2$. 

Calculate the percentage composition of Potassium chlorate, ${\mathrm{KClO}}_3$. 

Find the empirical formula of the compound with the following percentage composition: 

$\mathrm{Pb}=62.5\%, \mathrm{N}=8.5\%, \mathrm{O}=29\%$.

Calculate the mass of iron in $10 \mathrm{kg}$ of iron ore which contains $80\%$ of pure ferric oxide.

If the empirical formula of two compounds is $\mathrm{CH}$ and their vapour densities are $13$ and $39$ respectively, find their molecular formula.

Find the empirical formula of a compound containing $17.64\%$ hydrogen and $82.35\%$ nitrogen.

On analysis, a substance was found to contain:

 $\mathrm{C}=54.54\%, \mathrm{H}=9.09\%, \mathrm{O}=36.36\%$

The vapour density of the substance is $44$, calculate (a) its empirical formula (b) its molecular formula. 

An organic compound, whose vapour density is $45$, has the following percentage composition, 

$\mathrm{H}=2.22\%, \mathrm{O}=71.19\%$ and remaining carbon. Calculate: (a) its empirical formula, (b) its molecular formula.