The rate of chemi-sorption:

Options

A. decreases with increase in pressure
B. is independent of pressure
C. is maximum at one atmospheric pressure
D. increases with increase in pressure

Answer

To solve the question regarding the rate of chemisorption, we need to analyze the factors that influence this process. Here’s a step-by-step breakdown:

### Step 1: Understand Chemisorption
Chemisorption is a type of adsorption where new chemical bonds are formed between the adsorbate (the substance being adsorbed) and the adsorbent (the surface on which adsorption occurs). This process involves the transfer or sharing of electrons, leading to the formation of stable chemical bonds.

**Hint:** Remember that chemisorption involves a chemical change and bond formation, unlike physisorption, which is a physical process.

### Step 2: Identify Factors Affecting Chemisorption Rate
The rate of chemisorption is influenced by several factors, including:
- The flux of the chemical species (the number of molecules striking the surface per unit area per unit time).
- The pressure of the gas (which affects the concentration of the adsorbate).

**Hint:** Consider how increasing the concentration of the adsorbate might affect the rate of adsorption.

### Step 3: Analyze the Effect of Pressure
- An increase in pressure generally leads to an increase in the concentration of the adsorbate, which would intuitively suggest that the rate of chemisorption might increase.
- However, the video transcript indicates that at higher pressures, the rate of chemisorption actually decreases. This is because the increased pressure can lead to a reduction in the diffusion length of the species, which means that the molecules have less space to move and interact with the surface.

**Hint:** Think about how crowded conditions might affect the movement and interaction of molecules with the surface.

### Step 4: Conclusion on the Rate of Chemisorption
From the analysis, we conclude that:
- The rate of chemisorption decreases with an increase in pressure due to the reduced diffusion length of the species.
- Therefore, the correct answer to the question regarding the rate of chemisorption is that it decreases with an increase in pressure.

**Hint:** Always consider the physical implications of changes in pressure on molecular behavior when discussing adsorption processes.

### Final Answer
The rate of chemisorption decreases with an increase in pressure.