Question

The concentration in $\text{g/L}$ of a solution of cane sugar (Molecular weight $ \, \text{=} \, \text{342)}$ which is isotonic with a solution containing $\text{6} \, \text{g}$ of urea $\text{(Molecular weight} \text{=} \, \text{60)}$ per litre is

• A. 3.42
• B. 34.2
• C. 5.7
• D. 19

Answer 1

Answer: (B)

The two solution should have same molar concentration for being isotonic.

Molar concentration of cabe sugar = Molar concentration of urea $= \frac{6}{6 0} = \text{0.1} \text{ mol/L}$

concentration of cane sugar in $\text{g/L}$

$\text{= molar concentration } \times \text{ molecular weight}$

$\text{=} \, \text{0} \text{.1} \,\times \, \text{342} \, \text{=} \, \text{34} \text{.2}$