Question

Benzene contains 92.3% Carbon and rest of hydrogen.If the molecular mass of Benzene is 78.
1. Find the percentage of hydrogen in Benzene.
2. Calculate the ratio of moles of Carbon and Hydrogen atom in Benzene.
​3. Calculate its empirical formula and then its molecular formula.

Answer 1

1. If benzene has 92.3% of carbon, then mass of carbon in benzene = $\frac{92.3}{100}\times 78$=71.99.

Mass of Hydrogen = 78 - 71.99 = 6.01.

2. Moles of C: Moles of H = $\frac{{\displaystyle \frac{71.99}{12}}}{{\displaystyle \frac{6.01}{1}}}=\frac{71.99}{12}\times \frac{1}{6.01}=0.9$

3. Empirical Formula = CH
Molecular formula = C₆H₆