Question

What is the percentage of carbon in urea?
(Atomic mass $C=12$, $H=1$, $N=14$, $O=16$)

• A. $20\%$
• B. $26.6\%$
• C. $6.67\%$
• D. $46.0\%$

Answer 1

Answer: (A)

Molar mass of urea (i.e. $N{H}_{2}CON{H}_2)$

$=2\times$ atomic mass of $N+4\times$ atomic mass of $H+1\times$ atomic mass of $O+1\times$ atomic mass of $C$.

$=2\times 14+4\times 1+1\times 16+1\times 12=60g$

As we know that,

Percentage or mass $\%$ of an element

$=\frac{\text{ Mass of that element in the compound }}{\text{ Molar mass of the compound }}\times 100$

$\therefore$ Percentage of $C=\frac{1\times 12}{60}\times 100=20\%$