Question

$0.9$ gm of a volatile solid organic compound (molecular weight$=90$), containing carbon, hydrogen and oxygen, was heated with $224$ ml oxygen at $1$ atm and $273$ K. After combustion, the total volume of gases was $560$ ml at $1$ atm and $273$ K. On treatment with $KOH$, the volume decreased to $112$ ml. The formula of the organic compound is $C_x{H}_y{O}_z$. Find $(x+y+z)/2$.

Answer 1

$C_x{H}_y{O}_z+\frac{(2x+0.5y-z)}{2}{O}_2\to xC{O}_2+\frac{y}{2}{H}_{2}O$
The number of moles of hydrocarbon $=\frac{0.9}{90}=0.01$
The number of moles of carbon dioxide $=\frac{448}{22400}=0.02$
Hence, $x=\frac{0.02}{0.01}=2$
Total volume after combustion is 560 ml.
Total number of moles after combustion $=\frac{560}{22400}=0.025$
The increase in the number of moles $=0.025-0.02=0.005$. It is equal to $\frac{z-3}{10}$
Hence, $z=3$
Hence, $x+y+z=18$