Question

d) Consider the following statements
Statement 1-finely divided substance is less effective as an adsorbent.
Statement 2-In chemisorptions chemical bonds are formed but not in physisorptions.
i)both statement 1 and statement 2 are correct
ii)only statement 1 is correct
iii)only statement 2 is correct
iv)both statement 1 and statement 2 are incorrect​

Answer 1

Answer:

Adsorption is the phenomenon of accumulation of large number of molecular species at the surface of liquid or solid phase in comparison to the bulk.

It is of following two types:

1. Physical Adsorption (Physisorption)

2. Chemical Adsorption (Chemisorption)

Adsorption processes take place by adsorbate getting adsorbed on adsorbent.Forces of attraction exist between adsorbate and adsorbent and due to these forces of attraction, heat energy is released. So, all adsorptions are exothermic processes.

1. Physical Adsorption:

When the force of attraction existing between adsorbate and adsorbent are weak Vanderwaal forces of attraction, the process is called Physical Adsorption or Physisorption. Physical Adsorption takes place with formation of multilayer of adsorbate on adsorbent. It has low enthalpy of adsorption i.e. ΔH

adsorption

is 20−40 kJ/mol.

It takes place at low temperature below boiling point of adsorbate.As the temperature increases in, process of Physisorption decreases.

It does not require any energy of Activation and is generally instantaneous.

2.Chemical Adsorption:

When the force of attraction existing between adsorbate and adsorbent are chemical forces of attraction or chemical bond, the process is called Chemical Adsorption or Chemisorption. Chemisorption takes place with formation of unilayer of adsorbate on adsorbent. It has high enthalpy of adsorption i.e. ΔH

adsorption

is 200−400 kJ/mol.

It can take place at all temperature. With the increases in temperature, Chemisorption first increases and then decreases.

It requires some energy of Activation and is hence slow.

Hence Answer is Option AandD