Match the List-I with List-II.
| List-I Terms | List-II Units |
| (A) Cell constant | (I) ohm−1 |
| (B) Molar conductance | (II) ohm−1 cm−1 |
| (C) Specific conductance | (III) ohm−1 cm2 mol−1 |
| (D) Conductance | (IV) cm−1 |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) - (IV), (B) - (III), (C) - (II), (D) - (I)
All four quantities come from the resistance of the solution between two electrodes of area A placed a distance l apart, R = ρl/A. Working in ohm and cm, each unit is derived from its defining equation:
(A) Cell constant — This matches (IV) cm−1. The cell constant G* depends only on the geometry of the cell.
\( \displaystyle G^{*}=\frac{l}{A}\ \Rightarrow\ \frac{\mathrm{cm}}{\mathrm{cm^{2}}}=\mathrm{cm^{-1}} \)
(B) Molar conductance — This matches (III) ohm−1 cm2 mol−1. It is the conductivity divided by the molar concentration (c in mol cm−3).
\( \displaystyle \Lambda_m=\frac{\kappa}{c}\ \Rightarrow\ \frac{\mathrm{ohm^{-1}\,cm^{-1}}}{\mathrm{mol\,cm^{-3}}}=\mathrm{ohm^{-1}\,cm^{2}\,mol^{-1}} \)
(C) Specific conductance — This matches (II) ohm−1 cm−1. Specific conductance (conductivity) is the conductance multiplied by the cell constant.
\( \displaystyle \kappa=G\times\frac{l}{A}\ \Rightarrow\ \mathrm{ohm^{-1}}\times\mathrm{cm^{-1}}=\mathrm{ohm^{-1}\,cm^{-1}} \)
(D) Conductance — This matches (I) ohm−1. Conductance is the reciprocal of resistance.
\( \displaystyle G=\frac{1}{R}\ \Rightarrow\ \mathrm{ohm^{-1}} \)
Shortcut: The pair (A)–(IV) appears only in Option (2).
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| 25-05 S1 | 13-05 S1 | – | – | – |