Calculate the percentage of carbon, hydrogen and oxygen in ethanol (${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$).

An inorganic salt on analysis gave the following percentage composition: $\mathrm{Pb}=62.6$, $\mathrm{N}=8.4$, $\mathrm{O}=29$.

What is empirical formula of the compound? Also name the compound. (At. Mass: $\mathrm{Pb}=207, \mathrm{N}=14, \mathrm{O}=16$).

A sample of a salt has the percentage composition: $\mathrm{Fe}=36.76; \mathrm{S}=21.11; \mathrm{O}=42.14;$

Calculate the empirical formula of the compound. (At. Mass: $\mathrm{Fe}=56; \mathrm{S}=32; \mathrm{O}=16;$).

Calculate the empirical formula of a mineral having the following compositions. 

$\mathrm{CaO}=48.0 \%; {\mathrm{P}}_2{\mathrm{O}}_5=41.3 \%; {\mathrm{CaCl}}_2=10.7 \%;$

A crystalline salt when heated becomes anhydrous and loses $51.2 \%$ of its weight. The anhydrous salt on analysis gave the percentage composition as:

$\mathrm{Mg}=20.0 \%; \mathrm{S}=26.66 \%; \mathrm{O}=53.33 \%;$ Calculate the molecular formula of the anhydrous salt and the crystalline salt. Molecular mass of the anhydrous salt is $120$.

A compound containing carbon, hydrogen and oxygen gave the following analytical data: $\mathrm{C}=40.0 \%$ and $\mathrm{H}=6.67 \%$.

Calculate the molecular formula of the compound if its molecular mass is $180$.