Question

Question 7.3 At a certain temperature and total pressure of 105 Pa, iodine vapour contains 40% by volume of I atoms

I2(g) <---> 2I(g)

Calculate Kp for the equilibrium.

Class XI Equilibrium Page 224

Answer 1

Given, I2(g) <=> 2I(g)
I atoms in iodine vapour = 40% by volume
it means I2 molecule in iodine vapour = (100 - 40)% = 60% by volume.

now, we have to find out partial pressure of I atoms and I2 molecules .
partial pressure = mole fraction × total pressure

so, partial pressure of I atoms = 0.4 × 10^5 Pa
partial pressure of I2 molecules = 0.6 × 10^5 Pa

now, A/C to question,
Kp = P(I)²/P(I2)
= (0.4 × 10^5)²/(0.6 × 10^5)
= 0.267 × 10^5 Pa
= 2.67 × 10⁴ Pa