Question

If $0.2gram$ of an organic compound containing carbon, hydrogen and oxygen on combustion, yielded $0.147gram$ carbon dioxide and $0.12gram$ water, what will be the content of oxygen in substance?

• A. $83.23\%$
• B. $78.45\%$
• C. $73.29\%$
• D. $89.50\%$

Answer 1

Answer: (C)

$\underset{0.2g}{\text{Organic compound}}+O_2\to \underset{0.02g}{H_{2}O}+\underset{0.147g}{C{O}_2}$+ heat

Percentage of carbon $=\frac{12}{44}\times \frac{\text{ mass of }C{O}_2}{\text{ mass of compound }}\times 100$

$=\frac{12}{44}\times \frac{0.147}{0.2}\times 100=20.04\%$

Percentage of Hydrogen $=\frac{2}{18}\times \frac{\text{ mass of }{H}_{2}O}{\text{ mass of compound }}\times 100$

$=\frac{2}{18}\times \frac{0.12}{0.2}\times 100=6.67\%$

Percentage of oxygen $=100-(6.67+20.04)=73.29\%$