Which of the following is not considered as absorption 

Options

A. chalk piece dipped in ink
B. sponge placed in water
C. finely divided charcoal stirred with dilute acetic acid
D. `H_(2)` gas in contact with finely divided Pd

Answer

To determine which of the following options is not considered adsorption, we need to analyze each option provided:

1. **Chalk piece dipped in ink**:
- In this case, the ink penetrates the surface of the chalk piece. This process involves the ink molecules being taken up by the chalk, which is characteristic of absorption. Therefore, this option is considered absorption.

2. **Chalk sponge placed in water**:
- A sponge, when placed in water, absorbs the water into its structure. This is also a clear example of absorption, as the water molecules fill the pores of the sponge. Hence, this option is also considered absorption.

3. **Finely divided charcoal stirred with dilute acetic acid**:
- When charcoal is mixed with dilute acetic acid, the acetic acid molecules adhere to the surface of the charcoal particles. This process is known as adsorption, where molecules stick to the surface rather than being absorbed into the bulk of the material. Therefore, this option is considered adsorption.

4. **Hydrogen gas in contact with finely divided palladium**:
- In this scenario, hydrogen gas molecules adhere to the surface of the palladium. This is a classic example of adsorption, as the hydrogen does not penetrate into the palladium but rather sticks to its surface. Therefore, this option is also considered adsorption.

After analyzing all the options, we find that the first three options involve absorption, while the last option involves adsorption.

Thus, the correct answer to the question "Which of the following is not considered as absorption?" is:

**Answer: Hydrogen gas in contact with finely divided palladium (adsorption)**.