Question

The percentage of carbon in 'Z' is (At.wt. C = 12 u, H = 1 u, N = 14 u, O = 16 u)

• A. 71.3%
• B. 51.3%
• C. 61.3%
• D. 48.3%

Hint:

Calculate percentage composition by dividing total atomic mass of element by molar mass of compound.

Answer 1

The Correct Option is C

Calculate molecular weight of Z and percentage of carbon as: \[ %\text{C} = \frac{\text{mass of carbon}}{\text{molar mass}} \times 100 \] Molecular formula of Z corresponds to benzene ring with methyl group, so: C: 7 atoms \(\times 12 = 84\) Total molar mass (benzene ring + substituents) \(\approx 137\) Percentage C = \(\frac{84}{137} \times 100 = 61.3%\)