Which of the following decrease with increase in concentration?

Options

A. conductance
B. specifci conductance
C. Molar conductance
D. Conductivity

Answer

To solve the question "Which of the following decrease with increase in concentration?", we need to analyze the properties mentioned and their relationship with concentration.

### Step-by-Step Solution:

1. **Understanding Conductance**:
- Conductance refers to the ability of an electrolyte solution to conduct electricity, which depends on the movement of ions in the solution.
- As the concentration of an electrolyte increases, the number of ions present also increases, leading to a higher force of attraction between the ions.

**Hint**: Remember that conductance is related to the movement of ions; more ions can mean more interactions.

2. **Effect of Concentration on Conductance**:
- With increased concentration, ions are closer together, which increases the force of attraction between them. This can lead to a decrease in the mobility of the ions.
- As the mobility of ions decreases, the overall conductance of the solution also decreases.

**Hint**: Think about how increased attraction between ions affects their ability to move freely.

3. **Understanding Specific Conductance (Conductivity)**:
- Specific conductance (or conductivity) is defined as the conductance of a solution per unit volume. It generally increases with concentration because more ions are available to carry charge.
- Therefore, specific conductance does not decrease with an increase in concentration.

**Hint**: Specific conductance is about the amount of ions per volume; more ions typically mean higher conductivity.

4. **Understanding Molar Conductance**:
- Molar conductance is defined as the conductance of the solution divided by the number of moles of solute in a given volume. It is influenced by dilution.
- As concentration increases, the volume of the solution remains constant while the number of moles increases, leading to a decrease in molar conductance.

**Hint**: Molar conductance is inversely related to concentration; think about how dilution affects it.

5. **Conclusion**:
- From the analysis, we can conclude that:
- Conductance decreases with an increase in concentration (Option A).
- Molar conductance also decreases with an increase in concentration (Option C).
- Specific conductance (conductivity) does not decrease with an increase in concentration.

### Final Answer:
- The properties that decrease with an increase in concentration are **Conductance (Option A)** and **Molar Conductance (Option C)**.