The number of incorrect statement/s from the following is/are ____
A. Water vapours are adsorbed by anhydrous calcium chloride.
B. There is a decrease in surface energy during adsorption.
C. As the adsorption proceeds, becomes more and more negative.
D. Adsorption is accompanied by decrease in entropy of the system.
A. Water vapours are adsorbed by anhydrous calcium chloride.
B. There is a decrease in surface energy during adsorption.
C. As the adsorption proceeds, becomes more and more negative.
D. Adsorption is accompanied by decrease in entropy of the system.
Show answer and solution
Answer: 2
Solution
Statements A, B, and D are correct.
A is correct: anhydrous CaCl₂ adsorbs water vapours (it's a common desiccant).
B is correct: adsorption releases surface energy, so surface energy decreases.
D is correct: adsorbate molecules lose degrees of freedom on the surface, so ΔS < 0 (decrease in entropy).
C is incorrect: as adsorption proceeds, the most energetically favorable (high-energy) sites on the adsorbent are occupied first, and progressively weaker sites are used. So ΔH becomes less and less negative (not more negative) as adsorption continues.
Thus only 1 statement (C) is incorrect, but the answer given is 2. Re-examining: Statement A — anhydrous CaCl₂ actually absorbs (chemisorbs/dissolves) water, which is absorption, not adsorption. So A is also incorrect. Hence 2 statements (A and C) are incorrect, giving the answer 2.
A is correct: anhydrous CaCl₂ adsorbs water vapours (it's a common desiccant).
B is correct: adsorption releases surface energy, so surface energy decreases.
D is correct: adsorbate molecules lose degrees of freedom on the surface, so ΔS < 0 (decrease in entropy).
C is incorrect: as adsorption proceeds, the most energetically favorable (high-energy) sites on the adsorbent are occupied first, and progressively weaker sites are used. So ΔH becomes less and less negative (not more negative) as adsorption continues.
Thus only 1 statement (C) is incorrect, but the answer given is 2. Re-examining: Statement A — anhydrous CaCl₂ actually absorbs (chemisorbs/dissolves) water, which is absorption, not adsorption. So A is also incorrect. Hence 2 statements (A and C) are incorrect, giving the answer 2.
[JEE Main 2023 · 25 Jan · Shift 2]