Ncert Exercises & Solutions

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

I2 (g) 2I (g)

Calculate Kp for the equilibrium.

The partial pressure of I atoms,

P_{I} = \frac{40}{100} \times p_{total} = \frac{40}{100} \times 10^{5} = 4 \times 10^{4} Pa Partial pressure of I_{2} molecules, P_{I_{2}} = \frac{60}{100} \times p_{total} = \frac{60}{100} \times 10^{5} = 6 \times 10^{4} Pa Now, for the given reaction, K_{p} = \frac{{(pI)}^{2}}{p_{I_{2}}} = \frac{{(4 \times 10^{4})}^{2} {Pa}^{2}}{6 \times 10^{4} Pa} = 2.67 \times 10^{4} Pa