Question

Butyric acid contains only C, H and O. A 4.24 mg sample of butyric acid is completely burned. It gves 8.45 mg of carbon dioxide $\left(C{O}_2\right)$ and 3.46 mg of water. What is the mass percentage of C, H and O in butyric acid respectively?

• A. $54.35,9.06,36.59$
• B. $36.59,54.35,9.06$
• C. $54.35,36.59,9.06$
• D. $9.06,54.35,36.59$

Answer 1

The correct option is A $54.35,9.06,36.59$

Total mass of sample=$4.24mg$
Total $C{O}_2$ produced=$8.45mg$
Atomic mass of carbon=$12g$
Atomic mass of $C{O}_2$=$44g$
$\%C=\frac{12\times 8.45}{44\times 4.24}\times 100=54.35\%$

Total water produced=$3.46mg$
Mass of $H_2$=$2g$
Mass of $H_{2}O=18g$
$\%H=\frac{2\times 3.46}{18\times 4.24}\times 100=9.06\%$ $\%O=[100-54.35-9.06]=36.59\%$