Question

The empirical formula of a non-electrolyte is $CH_2O$. A solution containing $6 \,g$ of the compound exerts the same osmotic pressure as that of $0.05\, M$ glucose solution at the same temperature. The molecular formula of the compound is

• A. $CH _{2} O$
• B. $C _{2} H_{4} O _{2}$
• C. $C_4H_8O_4$
• D. $C_3H_{6}O_3$

Answer 1

Answer: (C)

Solutions having same osmotic pressure, at a given temperature, have same concentration.
Concentration of compound = concentration of glucose
$
\begin{array}{l}
\frac{6}{ M \times 1}=0.05 \\
M =\frac{6}{0.05}=120 \\
\left( CH _{2} O \right)=12+2+16=30 \\
n =\frac{\text { molecular mass }}{\text { empirical formula mass }}=\frac{120}{30}=4
\end{array}
$
Hence, Molecular formula $\left( CH _{2} O \right)_{4}= C _{4} H _{8} O _{4}$