Question

Which of the following statements are correct about chemisorption?

• It is highly specific in nature.

• It is reversible in nature.

• It depends on nature of gas.

• It is unilayer adsorption.
The correct answer is:

• A. I \& II only
• B. I \& IV only
• C. I, II \& IV only
• D. I, III \& IV only

Hint:

To quickly remember the properties of chemisorption:

• Strong chemical bond formation.

• Highly specific in nature.

• Usually irreversible.

• Forms only a monolayer.

• Depends on the chemical nature of the gas and adsorbent.
A useful memory aid is: “Specific, Strong, Single-layer” for chemisorption.

Answer 1

The Correct Option is D

Step 1: Recall what chemisorption is.
Chemisorption is adsorption where the gas forms real chemical bonds with the solid surface. Because true bonds form, it has special, strong-bond features. We check each statement against these features.
Step 2: Check statement I (specific).
Since chemical bonds depend on the matching chemistry of gas and surface, only certain gases stick to a given solid. So chemisorption is highly specific. Statement I is correct.
Step 3: Check statement II (reversible).
The bonds formed are strong, so a lot of energy is needed to pull the gas off. The process does not reverse easily under normal conditions. So chemisorption is generally irreversible. Statement II is incorrect.
Step 4: Check statement III (depends on nature of gas).
Because chemical bonding is involved, the amount adsorbed depends strongly on the chemical nature of the gas. So statement III is correct.
Step 5: Check statement IV (single layer).
Once a gas molecule bonds to an active site, no more can pile on that site. So chemisorption forms only one layer (monolayer). Statement IV is correct.
Step 6: Combine the correct ones.
Statements I, III and IV are correct, while II is wrong. So the answer is \[ \boxed{\text{I, III and IV only}} \]