Question

An organic compound contains $69\%$ carbon and $4.8\%$ hydrogen, the remainder being oxygen. What will be the masses of carbon dioxide and water produced when $0.20g$ of this substance is subjected to complete combustion.

• A. $0.69g$ and $0.048g$
• B. $0.506g$ and $0.086g$
• C. $0.345g$ and $0.024g$
• D. $0.91g$ and $0.72g$

Answer 1

Answer: (B)

$\%C=\frac{12}{44}\times \frac{\text{mass of CO2 formed}}{\text{mass of substance taken}}\times 100$
$69=\frac{12}{44}\times \frac{\text{Mass of CO2 formed}}{0.2}\times 100$
$\therefore$ Mass of $C{O}_2$ formed $=\frac{69\times 44\times 0.2}{12\times 100}=0.506g$
$\%H=\frac{2}{18}\times \frac{\text{mass of H2O formed}}{\text{mass of substance taken}}\times 100$
$4.8=\frac{2}{18}\times \frac{x}{0.2}\times 100$
$x=\frac{4.8\times 18\times 0.1}{100}$
$=0.086g$