Question

If $0.2\, gram$ of an organic compound containing carbon, hydrogen and oxygen on combustion, yielded $0.147\, gram$ carbon dioxide and $0.12\, gram$ 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)

$\underset{0.2\,g}{\text{Organic compound}}+O_{2} \to \underset{0.02\,g}{H_{2}O} + \underset{0.147\,g}{CO_{2}}$+ heat

Percentage of carbon $=\frac{12}{44} \times \frac{\text { mass of } CO _{2}}{\text { mass of compound }} \times 100$

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