Which one of the following characteristics is associated with adsorption ?

Options

A. `Delta G and Delta S` are nagative but `Delta H` is positive
B. `Delta G ` is nagative but `Delta H and Delta S` are positive
C. `Delta G, Delta H and Delta S` all are nagative
D. `Delta G and Delta H` are nagative but `Delta S` is positive

Answer

To determine which characteristic is associated with adsorption, we need to analyze the thermodynamic parameters involved in the process of adsorption. Here’s a step-by-step breakdown of the solution:

### Step 1: Understanding Adsorption
Adsorption is the process where molecules from a gas or liquid adhere to a solid surface. This process involves the accumulation of particles on the surface of a solid.

**Hint:** Remember that adsorption is different from absorption; it specifically refers to the accumulation of particles on a surface.

### Step 2: Analyzing Gibbs Free Energy (ΔG)
Gibbs free energy change (ΔG) indicates the spontaneity of a process. For adsorption to occur spontaneously, ΔG must be negative. This means that the process does not require external energy to proceed.

**Hint:** A negative ΔG indicates that the process is favorable and can occur without external energy.

### Step 3: Considering Enthalpy Change (ΔH)
Enthalpy change (ΔH) refers to the heat absorbed or released during the process. In the case of adsorption, energy is released as particles bond to the surface, indicating that the process is exothermic (ΔH is negative).

**Hint:** Exothermic processes release energy, which is a key characteristic of adsorption.

### Step 4: Evaluating Entropy Change (ΔS)
Entropy (ΔS) measures the randomness or disorder of a system. When particles adsorb onto a surface, the randomness decreases because the particles are more ordered on the surface compared to being in the gas phase. Therefore, ΔS is negative.

**Hint:** A decrease in randomness or disorder corresponds to a negative ΔS.

### Step 5: Conclusion
In summary, during the adsorption process:
- ΔG is negative (spontaneous process)
- ΔH is negative (exothermic process)
- ΔS is negative (decrease in randomness)

Thus, the characteristic associated with adsorption is that all three thermodynamic parameters (ΔG, ΔH, and ΔS) are negative.

**Final Answer:** The characteristic associated with adsorption is that ΔG, ΔH, and ΔS are all negative.