For strong electrolytes, Λ_m increases with dilution and is represent…

The correct answer is Option (3) → (A), (B), (C) and (D)

For a strong electrolyte the molar conductivity rises slowly on dilution, because the ions move apart and the interionic attractions that hold them back become weaker. This is described by

    \( \displaystyle \Lambda_m = \Lambda_m^{0} - A\,c^{1/2} \)

A plot of \( \Lambda_m \) against \( c^{1/2} \) is a straight line with intercept \( \Lambda_m^{0} \) and slope \( -A \). The constant A measures how strongly the ions are slowed down by one another, so it depends on what the ions are and on the medium they move in.

• (A) Nature of solvent. — Correct. The solvent (through its dielectric constant and viscosity) decides how strongly the ions attract one another and how freely they move.

• (B) Temperature. — Correct. The value of A holds for a given temperature; a change in temperature changes ionic motion and the viscosity of the solvent.

• (C) Charges on cation and anions produced. — Correct. Ions of higher charge attract one another more strongly, so A is larger for them.

• (D) Type of electrolyte. — Correct. The type (1-1 such as NaCl, 2-1 such as \( \ce{CaCl2} \), 2-2 such as \( \ce{MgSO4} \)) is fixed by the charges on the ions, and all electrolytes of one type have the same value of A.

NCERT (2026-27 edition):
Strong Electrolytes – “For strong electrolytes, Λ_m increases slowly with dilution and can be represented by the equation: Λ_m = Λ°_m – A c^½ … It can be seen that if we plot … Λ_m against c^1/2, we obtain a straight line with intercept equal to Λ°_m and slope equal to ‘–A’. The value of the constant ‘A’ for a given solvent and temperature depends on the type of electrolyte i.e., the charges on the cation and anion produced on the dissociation of the electrolyte in the solution. Thus, NaCl, CaCl₂, MgSO₄ are known as 1-1, 2-1 and 2-2 electrolytes respectively. All electrolytes of a particular type have the same value for ‘A’.”