# Molar Conductivity Calculator

Λm = κ/c in S·cm²/mol and S·m²/mol, with optional α = Λm/Λ°m and Ka for weak electrolytes.

> Canonical page: https://elysiatools.com/en/tools/molar-conductivity

- **Category:** Science & Education

- **Keywords:** molar conductivity, lambda m, kappa over c, degree of dissociation, limiting molar conductivity, weak electrolyte ka

## Overview

The Molar Conductivity Calculator determines electrolyte molar conductivity (Λm = κ/c) in S·cm²/mol and S·m²/mol from measured solution conductivity and concentration. By optionally providing the limiting molar conductivity (Λ°m), it also computes the degree of dissociation (α) and the acid dissociation constant (Ka) for 1:1 weak electrolytes via Ostwald's dilution law.

## Inputs

- **Conductivity κ** (number): e.g. 1412
- **Conductivity unit** (select)
- **Concentration c** (number): e.g. 0.01
- **Concentration unit** (select)
- **Limiting molar conductivity Λ°m (S·cm²/mol, optional)** (number): e.g. 149.9 (KCl) or 390.7 (HAc)

## When to use

- Converting raw electrical conductivity measurements into normalized molar conductivity values across various unit systems.
- Evaluating electrolyte behavior to differentiate between strong electrolytes and weakly dissociating species.
- Calculating the degree of dissociation (α) and equilibrium constant (Ka) for weak acids or bases using conductometric data.

## How it works

- Enter the measured electrolytic conductivity (κ) and select the appropriate unit (µS/cm, mS/cm, or S/m).
- Specify the solution concentration (c) and select its unit (mol/L, mmol/L, or µmol/L).
- Optionally enter the limiting molar conductivity (Λ°m) in S·cm²/mol to determine dissociation metrics.
- The tool normalizes units, calculates Λm = κ/c, and determines α = Λm/Λ°m and Ka = cα²/(1−α) when Λ°m is provided.

## Use cases

- Physical chemistry lab students analyzing conductivity data to find the Ka of weak acids like acetic acid.
- Researchers validating ionic mobility and Kohlrausch limiting conductivity laws for standard salts such as KCl.
- Analytical chemists converting conductivity probe readings into normalized molar metrics across varying sample dilutions.

## Frequently asked questions

### What is the formula used to calculate molar conductivity?

Molar conductivity is calculated as Λm = κ/c, where κ is electrolytic conductivity and c is molar concentration.

### Which units can be used for conductivity and concentration?

Conductivity supports µS/cm, mS/cm, and S/m. Concentration supports mol/L (M), mmol/L (mM), and µmol/L (µM).

### How is the degree of dissociation (α) determined?

When limiting molar conductivity (Λ°m) is provided, the tool calculates the degree of dissociation as α = Λm / Λ°m.

### How does the calculator compute the dissociation constant (Ka)?

For weak 1:1 electrolytes, Ka is computed using Ostwald's dilution law: Ka = (c · α²) / (1 − α).

### In what units are the molar conductivity results displayed?

Results are provided in both standard CGS units (S·cm²/mol) and SI units (S·m²/mol).

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