Question

One mole each of urea, glucose and sodium chloride were dissolved in one litre of water. Equal osmotic pressure will be produced by solutions of:

• A. glucose and sodium chloride
• B. urea and glucose
• C. sodium chloride and urea
• D. none of the above

Answer 1

Answer: (B)

urea and glucose

Osmotic pressure is a colligative property which depends upon the number of moles of solute present in the solution.

$\Pi =iCRT$

NaCl, when dissolved in water, gives 2 moles of ions ( $N{a}^{+}$ and $C{l}^{-}$) on dissociation, as one mole of NaCl is dissolved.

$NaCl⟶N{a}^{+}+C{l}^{-}$ $i=2$

But urea and glucose do not ionise. They are non-electrolytes. So, the Van't Hoff factor of both urea and glucose will be $i=1$.

Therefore, equal osmotic pressure will be produced by the solution of urea and glucose only.

Hence, option B is correct.