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 $0.20 \,g$ of this substance is subjected to complete combustion.

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

Answer 1

Answer: (B)

$\% C=\frac{12}{44}\times\frac{\text{mass of $CO_{2}$ formed}}{\text{mass of substance taken}}\times100$
$69=\frac{12}{44}\times\frac{\text{Mass of $CO_{2}$ formed}}{0.2}\times100$
$\therefore $ Mass of $CO_{2}$ formed $=\frac{69\times44\times0.2}{12\times100}=0.506\, g$
$\% H=\frac{2}{18}\times\frac{\text{mass of $H_{2}O$ formed}}{\text{mass of substance taken}}\times100$
$4.8=\frac{2}{18}\times\frac{x}{0.2}\times100$
$x=\frac{4.8\times18\times0.1}{100}$
$=0.086\,g$