Question

An organic compound on analysis gave the following composition.

Carbon = 40%, Hydrogen = 6.66%, Oxygen = 53.34%. Calculate its molecular formula, if molecular mass is 90.

Answer 1

By using element percentage composition - Atomic mass - Atomic ratio

Carbon $⟶40\%÷12=\frac{40}{12}=3.33$

Hydrogen $⟶6.66\%÷1=\frac{6.66}{1}=6.66$

Oxygen $⟶53.34\%÷16=\frac{40}{16}=3.33$

The least atomic ratio is 3.33.

For simplest ratio, we get C:H:O = 1:2:1

Empirical formula = $C{H}_{2}O$ of mass 30 g.

As molar mass = 60, Molecular formula = $(C{H}_{2}O{)}_2=C{H}_{3}COOH$