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A 5% solution (wt/volume) of cane sugar is isotonic with 0.877% (wt/volume) of urea solution.Find the molecular weight of urea,if molecular weight of sugar is 342.

$\begin{array}{1 1}60\\50\\40\\80\end{array} $

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1 Answer

Isotonic solutions have same osmotic pressure at same temperature.
(or) $\large\frac{n_1}{V_1}$$ST =$$\large\frac{n_2}{V_2}$$ST$
(or) $\large\frac{n_1}{V_1}=\frac{n_2}{V_2}$
$\therefore C_1=C_2$
$\Rightarrow \large\frac{w_1}{m_1V_1}=\frac{w_2}{m_2V_2}$
$\therefore \large\frac{5}{342 \times \Large\frac{100}{1000}}=\frac{0.877}{m_2\times \Large\frac{100}{1000}}$
$\therefore m_2=\large\frac{0.877\times 342}{5}$
$\Rightarrow 59.99 \simeq 60$
answered Aug 6, 2014 by sreemathi.v