Two solutions 'A' and 'B' are taken and diluted. On dilution, it was seen that the limiting molar conductivity of 'B' increases to a smaller extent while that of 'A' increases to a much larger extent comparatively, which of the two is a strong electrolyte?

A

The correct answer is option 2. \(A\).

To understand why solution A is the strong electrolyte, let's break down the concept of molar conductivity and how Molar conductivity, often denoted as \(\Lambda \), is a measure of the ability of ions to conduct electricity in a solution. It depends on:

The number of ions present in the solution.

The mobility of those ions.

As a solution is diluted, the number of ions decreases because the total amount of solute remains constant while the volume increases. However, for strong electrolytes and weak electrolytes, the behavior on dilution is different.

Strong electrolytes (like NaCl, HCl, etc.) dissociate completely into their ions in solution. As a strong electrolyte is diluted, the number of ions decreases (because of the dilution), but the degree of dissociation increases. This means more solute dissociates into ions when the concentration decreases.

Due to this increased dissociation, the molar conductivity of the solution increases significantly as the solution is diluted.

Limiting molar conductivity \((\Lambda _0)\)of a strong electrolyte increases more noticeably with dilution because it eventually reaches the maximum dissociation at infinite dilution, where all ions are free to move.

Weak electrolytes (like acetic acid, ammonia, etc.) only partially dissociate into ions when dissolved in water. On dilution, the number of ions in the solution decreases, but the extent of dissociation increases only slightly because the electrolyte is only weakly dissociated even at higher dilutions.

Therefore, for weak electrolytes, the molar conductivity increases less significantly upon dilution compared to strong electrolytes.

Their limiting molar conductivity increases to a smaller extent because they do not dissociate as much.

Applying this to the given solutions:

Solution A: The fact that the limiting molar conductivity increases to a much larger extent upon dilution indicates that A is a strong electrolyte, as it dissociates extensively, and more ions are released into solution as it is diluted.

Solution B: The limiting molar conductivity increases to a smaller extent upon dilution, suggesting that B is a weak electrolyte, as it dissociates less, and dilution only slightly increases the ionization.

Conclusion:

A is a strong electrolyte because its conductivity increases significantly upon dilution due to greater dissociation.

B is a weak electrolyte because its conductivity increases less upon dilution, indicating only partial dissociation.

Therefore, the correct answer is A.