What would be the osmotic pressure (in atm) of this solution at 40.0 °C? Assume the density of the solution is the same as benzene, 0.877 g/mL.

Question

0.0711 kg of biphenyl (C₁₂H₁₀) is dissolve in benzene (C₆H₆) to create a solution with a total volume of 350.0 mL. (Assume the change in volume is negligible) What would be the osmotic pressure (in atm) of this solution at 40.0 °C? Assume the density of the solution is the same as benzene, 0.877 g/mL.

Answer 1

The equation to calculate osmotic pressure is

π = iMRT

π = osmotic pressure

i = van't Hoff factor = 1 since biphenyl is a non electrolyte

M = molarity = mols biphenyl / liter of solution (see below for calculation of M)

R = gas constant = 0.0821 Latm / Kmole

T = temperature in Kelvin = 40.0º + 273.15 = 313.15K

Calculation of M (moles / liter)

moles biphenyl = 0.0711 kg x 1000 g / kg x 1 mol / 154 g = 0.461 mols

liters of solution = 350.0 mls x 1 L / 1000 ml = 0.350 L

Molarity = M = 0.461 / 0.350 = 1.32 M

Calculating osmotic pressure

π = (1)(1.32)(0.0821)(313K)

π = 33.9 atm