What is the unit of molar conductivity (Λm)?

The correct answer is Option (1) → S cm² mol⁻¹

Molar conductivity is the conductivity κ divided by the molar concentration c. With κ in S cm⁻¹ and c in mol cm⁻³:

    \( \displaystyle \Lambda_m=\frac{\kappa}{c}=\frac{\mathrm{S\,cm^{-1}}}{\mathrm{mol\,cm^{-3}}}=\mathrm{S\,cm^{2}\,mol^{-1}} \)

NCERT (2026-27 edition):
2.4.1 Measurement of the Conductivity of Ionic Solutions – “… It, therefore, becomes necessary to define a physically more meaningful quantity called molar conductivity denoted by the symbol Λ_m (Greek, lambda). It is related to the conductivity of the solution by the equation:

    \( \displaystyle \text{Molar conductivity}=\Lambda_m=\frac{\kappa}{c} \qquad (2.21) \)

… If we use S cm^–1 as the units for κ and mol cm^–3, the units of concentration, then the units for Λ_m are S cm² mol^–1.”