The correct statement(s) pertaining to the adsorption of a gas on a solid surface is (are)
- (A)Adsorption is always exothermic.✓ Correct
- (B)Physisorption may transform into chemisorption at high temperature.✓ Correct
- (C)Physisorption increases with increasing temperature but chemisorption decreases with increasing temperature.
- (D)Chemisorption is more exothermic than physisorption, however it is very slow due to higher energy of activation.✓ Correct
Answer: (A), (B), (D)
Solution
Analysis of each statement:
(A) Correct: Adsorption is always exothermic because when gas molecules adsorb on a surface, bonds are formed, releasing energy ().
(B) Correct: At high temperatures, physisorption (weak van der Waals forces) can transform into chemisorption (chemical bond formation) as sufficient activation energy becomes available.
(C) Incorrect: Physisorption decreases with increasing temperature (exothermic process, Le Chatelier's principle). Chemisorption initially increases with temperature (needs activation energy) but may decrease at very high temperatures.
(D) Correct: Chemisorption involves chemical bond formation, making it more exothermic than physisorption. However, it requires higher activation energy, making it slower initially.
(A) Correct: Adsorption is always exothermic because when gas molecules adsorb on a surface, bonds are formed, releasing energy ().
(B) Correct: At high temperatures, physisorption (weak van der Waals forces) can transform into chemisorption (chemical bond formation) as sufficient activation energy becomes available.
(C) Incorrect: Physisorption decreases with increasing temperature (exothermic process, Le Chatelier's principle). Chemisorption initially increases with temperature (needs activation energy) but may decrease at very high temperatures.
(D) Correct: Chemisorption involves chemical bond formation, making it more exothermic than physisorption. However, it requires higher activation energy, making it slower initially.
JEE Advanced · 2011 · 10 Apr 2011 · Paper 1 · One or more correct options