The Question is from neet-chemistry surface-chemistry , and it was created by the author THIRUPATHI REDDY

Question

Which one of the following characteristics is associated with adsorption?

THIRUPATHI REDDY · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Thermodynamics of Adsorption
 **Related Topics**: Gibbs Free Energy, Enthalpy, Entropy
 **Prerequisites**: Understanding of thermodynamic parameters (ΔG, ΔH, ΔS) and their relationships.
## SOLUTION PATHWAY
**Given Information**:
The question asks about the thermodynamic characteristics of adsorption.
**Method & Steps**:
1. Analyze the thermodynamic parameters involved in adsorption.
  Reasoning: Adsorption is an exothermic process (heat is released), meaning ΔH is negative.  Also, adsorption leads to a decrease in randomness (molecules become more ordered on the surface), resulting in a negative ΔS.  Since ΔG = ΔH - TΔS, and both ΔH and ΔS are negative, ΔG will be negative at all temperatures, making the process spontaneous.
  Formula/Rule:  ΔG = ΔH - TΔS
2. Evaluate each option based on the thermodynamic principles of adsorption.
  Working: Let's examine each option:
        a. ΔG is negative, but ΔH and ΔS are positive: This is incorrect as adsorption is exothermic (ΔH<0) and leads to a decrease in entropy (ΔS<0).
        b. ΔG, ΔH, and ΔS are all negative: This correctly reflects the thermodynamic characteristics of adsorption.
        c. ΔG and ΔH are negative, but ΔS is positive: This is incorrect because ΔS should be negative for adsorption.
        d. ΔG and ΔS are negative, but ΔH is positive: This is incorrect; adsorption is exothermic (ΔH<0).
 3. Select the correct option.
  Result: Option B correctly represents the thermodynamic aspects of adsorption.
  Verification: The negative ΔG ensures spontaneity, the negative ΔH signifies exothermicity, and the negative ΔS reflects the decrease in randomness.
 ## OPTION ANALYSIS
A :x: Incorrect. Adsorption is exothermic (ΔH < 0) and results in a decrease in entropy (ΔS < 0).
B ✓: Correct.  Adsorption is spontaneous (ΔG < 0), exothermic (ΔH < 0), and leads to a decrease in entropy (ΔS < 0).
C :x: Incorrect. Entropy (ΔS) decreases during adsorption.
D :x: Incorrect. Adsorption is an exothermic process (ΔH < 0).
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the signs of ΔH and ΔS: Remember adsorption is exothermic (ΔH < 0) and leads to decreased entropy (ΔS < 0).
  2.Ignoring the relationship between ΔG, ΔH, and ΔS:  Use the Gibbs Free Energy equation (ΔG = ΔH - TΔS) to understand the overall spontaneity.
 **Quick Tips**:
  1.Think about the process: Adsorption involves molecules sticking to a surface, which is usually an exothermic and ordering process.
  2.Memorize the signs: ΔG < 0, ΔH < 0, ΔS < 0 for adsorption.

THIRUPATHI REDDY · Answer

$\Delta {\rm{G}}$ is negative but $\Delta {\rm{H}}$ and  $\Delta {\rm{S}}$ are positive

THIRUPATHI REDDY · Answer

The correct Option is "$\Delta {\rm{G}},\Delta {\rm{H}}\,{\rm{and}}\,\Delta \,{\rm{S}}$ all are negative"

THIRUPATHI REDDY · Answer

$\Delta {\rm{G}}\,{\rm{and}}\,\Delta {\rm{H}}$ are negative but $\Delta \,{\rm{S}}$  is positive

THIRUPATHI REDDY · Answer

$\Delta {\rm{G}}\,{\rm{and}}\,\Delta \,{\rm{S}}$ are negative but  $\Delta {\rm{H}}$ is positive

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