Question

A 0.050 MM solution of AlCl3 had an observed osmotic pressure of 3.85 atmatm at 20 ∘C . Calculate the van't Hoff factor iii for AlCl3.

Answer 1

The van't Hoff factor = 3.20

Step-by-step 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