Question

2 moles of a sparingly soluble salt PbCl2 dissociates in 1 litre solution to give 1 mole of Pb+2 ions, what is the osmotic pressure of the solution at 300 K?

Answer 1

Given:

No of moles of PbCl2, n = 2 moles

No of moles of Pb²⁺ = 1 moles

Volume of solution = 1 litre

Temperature, T = 300 K

To Find:

The osmotic pressure (Π) of the solution.

Calculation:

- The degree of dissociation, α = 1/2 = 0.5

- For PbCl2, n' = 3

- Also, α = (i - 1) / (n' - 1)

⇒ 0.5 = (i - 1) / (3 - 1)

⇒ i = 2

- The osmotic pressure is given as:

Π = inRT / V

⇒ Π = 2 × 2 × 0.082 × 300  / 1

⇒ Π = 98.4 atm

- So, the osmotic pressure (Π) of the given PbCl2 solution is 98.4 atm