Question

Percentage composition of hydrogen in benzene ($C_6{H}_6$) is :

• A. $8\%$
• B. $7.7\%$
• C. $50\%$
• D. $5\%$

Answer 1

The correct option is B $7.7\%$

Atomic mass of hydrogen = 1 u
Atomic mass of carbon = 12 u

Molecular mass of benzene $\left(C_6{H}_6\right)$ is $=(12\times 6)+(6\times 1)=78u$

Mass percentage of an element in a compound = $\frac{\text{Mass of an element}}{\text{Mass of compound}}\times 100$

Mass % of hydrogen in benzene = $\frac{6}{78}$ $\times 100$$=7.7\%$