JEE Chemistry 2023 Question with Solution

Given: Five statements about conductivity and molar conductivity are to be checked.

Find: The total number of correct statements.

Statement (A): Conductivity $\left(\kappa\right)$ depends on the number of ions per unit volume. On dilution, the number of ions per unit volume decreases, hence conductivity decreases for both strong and weak electrolytes.

Therefore, statement (A) is correct.

Statement (B): On dilution, the number of ions per unit volume decreases, although the total number of ions in solution may increase for weak electrolytes.

Hence, statement (B) is incorrect.

Statement (C): Molar conductivity $\left(\Lambda_m\right)$ is defined as conductivity of the solution containing one mole of electrolyte. On dilution, inter-ionic attraction decreases and mobility of ions increases, so molar conductivity increases.

Thus, statement (C) is correct.

Statement (D): For strong electrolytes, molar conductivity increases slightly with dilution, whereas for weak electrolytes it increases sharply due to increase in degree of dissociation.

Hence, statement (D) is correct.

Statement (E): For weak electrolytes, molar conductivity increases with dilution due to increase, not decrease, in degree of dissociation.

So, statement (E) is incorrect.

Correct statements are: (A), (C), and (D).

Therefore, the required numerical answer is $3$.

Given: Statements on dilution, conductivity, and molar conductivity.

Find: How many statements are correct.

Use the key facts:

• Conductivity decreases on dilution because ions per unit volume decrease.
• Molar conductivity increases on dilution.
• For weak electrolytes, the increase in molar conductivity is sharp because degree of dissociation increases.

Now eliminate:

• (A) correct
• (B) incorrect
• (C) correct
• (D) correct
• (E) incorrect

So the total number of correct statements is $3$.