Question

Analysis of vitamin $C$ shows that it contains $40.92\%$ carbon by mass, $4.58\%$ hydrogen and $54.50\%$ oxygen. Determine the empirical formula of vitamin $C$.

Answer 1

Vitamin $C$ contains $40.92\%$ carbon by mass, $4.58\%$ hydrogen and $54.50\%$ oxygen.

100 g of vitamin $C$ will contain 40.92 g C, 4.58 g, H and 54.50 g O.
Atomic masses of C, H and O are 12 g/mol, 1 g/mol and 16 g/mol respectively.

Number of moles of $C=\frac{40.92g}{12g/mol}=3.4mol$.

Number of moles of $H=\frac{4.58g}{1g/mol}=4.58mol$.

Number of moles of $O=\frac{54.50g}{16g/mol}=3.40mol$.

Mole ratio of C : H : O = 3.4 : 4.58 : 3.4 = 3 : 4 : 3

Empirical formula of vitamin $C$ is $C_3{H}_4{O}_3$.