Question

$A5\%$ solution of cane sugar $(M.W.=342)$ is isotonic with $1\%$ solution of substance $X$. The molecular weight of $X$ is

• A. $171.2$
• B. $68.4$
• C. $34.2$
• D. $136.2$

Answer 1

Answer: (B)

Being isotonic, molar concentration of cane sugar = molar concentration of substance $X$
$\frac{5}{342}\times \frac{1000}{100}$
$=\frac{1}{x}\times \frac{1000}{100}$
(let the molecular weight of $X=x$)
$x=\frac{342}{5}=68.4$