Question

Anhydrous CaCl₂ and silica gel differ in their behaviour towards moisture.

1. Identify the phenomenon taking place in both cases.

2. How is adsorption affected with pressure? Explain.

Answer 1

1. Anhydrous CaCl₂ absorbs moisture. The phenomenon is absorption. Silica gel absorbs moisture. The phenomenon is adsorption.

2. The rate of adsorption increases with increase in pressure. Freudlich’s adsorption expression is given by as \(\frac{x}{m}\) = kp^1/n (n > 1)

The graphical representation is,

At high pressure rate of adsorption attains a maximum value and after that pressure is having no influence. At low pressure, rate of adsorption is directly proportional to the pressure.