In a simple osmometer a column of solution rises until its hydrostatic pressure balances the osmotic pressure. The solution is $0.0050 mol L^{- 1}$ in a non-electrolyte at $300 K$ and its density is $1000 kg m^{- 3}$ . Take $g = 9.8 m s^{- 2}$ , $R = 8.314 J mo l^{- 1} K^{- 1}$ and neglect the height change of the solvent side. The height of the column is

Answer: C

c = 0.0050 mol L^{- 1} = 5.0 mol m^{- 3}

, so

π = c RT = 5.0 \times 8.314 \times 300 = 12471 Pa

. Balance with

ρ g h

h = π / (ρ g) = 12471/ (1000 \times 9.8) = 1.27 m