Answer:
The van't Hoff factor = 3.20
Explanation:
Step 1: data given
Osmotic pressure of a 0.050 M Solution is 3.85 atm
Temperature = 20.0 °C
Step 2:
Osmotic pressure depends on the molar concentration of the solute but not on its identity.
We can calculate the osmotic pressure by:
π = i.M.R.T
⇒ with π = osmotic pressure = 3.85 atm
⇒ with i = van 't Hoff factor = TO BE DETERMINED
⇒ with M = molar concentration of the solution =0.050 M
⇒ with R = gas constant =0.08206 L * atm / mol* K)
⇒ with T = Temperature of the solution =20°C = 293 K
i = π / M.R.T
i = 3.85 / 0.050*0.08206*293
i = 3.20
The theoretical Van't Hoff factor is 4:
AlCl3(aq) → Al^3+(aq) + 3Cl^-(aq)
AlCl3 dissociates in 1 mol Al^3+ + 3 moles Cl-
Due to the interionic atractions the Van't hoff factor is less than the theoretical value of 4
