Osmotic pressure of 0.25 M aqueous solution of urea at 300 K is

The correct answer is Option (2) → 6.225 bar

Osmotic pressure is a colligative property: it depends on the number of solute particles per unit volume. For a dilute solution:

    \( \displaystyle \pi = CRT \)

Urea is a non-electrolyte; it does not dissociate in water, so each molecule gives one particle (i = 1). To get the pressure in bar, R is taken as 0.083 L bar K⁻¹ mol⁻¹.

    \( \displaystyle \pi = 0.25\,\mathrm{mol\,L^{-1}} \times 0.083\,\mathrm{L\,bar\,K^{-1}\,mol^{-1}} \times 300\,\mathrm{K} \)

    \( \displaystyle \pi = 6.225\,\mathrm{bar} \)

So the osmotic pressure is 6.225 bar.

Shortcut: \( 0.25 \times 300 = 75 \), and \( 75 \times 0.083 = 6.225 \). The answer has to be near 6 bar, which rules out Options (1) and (3) at once.