Adsorption

Question 1

What are the two types of adsorption?

Answer 1

Physisorption, Chemisorption

Question 2

Give the factors which adsorbate quantity depends on

Answer 2

Adsorbate quantity depends on :

adsorbate type, adsorbent type, adsorbate concentration, adsorbent SA, temperature

Question 3

Define desorption

Answer 3

Reverse of adsorption => species evolved or removed from surface and concentration reduced

Question 4

Define Physisorption

Answer 4

Weak V.D.W forces

Question 5

Define chemisorption

Answer 5

Chemical bonds formed during process => only occurs if system able to form bonds

Question 6

Properties of physisorption

Answer 6

Properties:
low heat of adsorption,
fast rate of adsorption, uptake decreases with increasing temp,
easy desorption, adsorbate unchanged when desorbed,
non specific,
mono or multilayer coverage

Question 7

Why is physisorption always exothermic?

Answer 7

Always exothermic due to increased adsorbate order

Question 8

Properties of chemisorption

Answer 8

Properties:
high heat of adsorption,
slow rate of adsorption,
uptake increases as temp increases, difficult desorption, different desorption to original adsorptive, very specific, monolayer coverage

Question 9

Why is chemisorption endothermic?

Answer 9

Electron transfer between adsorbate and adsorbent –> chemical bonds formed