Question

On complete combustion, 0.5 g of an organic compound gave 0.2g of carbon dioxide and 0.4 g of water. Choose the correct statement(s) :

• A. $\%C$ in the compound is $10.9\%$
• B. $\%C$ in the compound is $20.5\%$
• C. $\%H$ in the compound is $15.5\%$
• D. $\%H$ in the compound is $8.89\%$

Answer 1

Answer: (A), (D)

$\%H$ in the compound is $8.89\%$

The given data is:
Mass of the organic compound $m=0.5g$
Mass of water $m_1=0.4$
Mass of carbon dioxide $m_2=0.2$
$\%H=\frac{2\times m_1\times 100}{18\times m}$

$\%H=\frac{2\times 0.4\times 100}{0.5\times 18}=8.89\%$

$\%C=\frac{12\times m_2\times 100}{44\times m}$

$\%C=\frac{12\times 0.2\times 100}{0.5\times 44}=10.91\%$

Theory :

$C_x{H}_y+(x+\frac{y}{4})O_2\stackrel{\Delta }{⟶}xC{O}_2+\left(\frac{y}{2}\right)H_{2}O$

Estimation of Carbon and Hydrogen:

A known mass of an organic compound is burnt in the presence of excess of oxygen and copper(II) oxide.
The products obtained after combustion are passed through anhydrous $CaC{l}_2$ and $KOH$ solution to absorb water and $C{O}_2$ respectively.