Electrical Conductivity
Ionic conductivity measures a solution's ability to carry current. Kohlrausch's law Λm = Λm° - K√c describes concentration dependence. Essential for water quality and electrolyte analysis.
Why This Chemistry Calculation Matters
Why: Conductivity indicates dissolved ion concentration—critical for water quality, electrolyte design, and analytical chemistry.
How: κ = 1/ρ; Λm = κ/c. For weak electrolytes use Kohlrausch: Λm = Λm° - K√c.
- ●κ = 1/ρ. High conductivity = low resistivity.
- ●Kohlrausch: Λm decreases with √c for weak electrolytes.
- ●Water quality: TDS correlates with conductivity.
- ●Cell constant: κ = K/R from resistance measurement.
Sample Examples
🔬 NaCl 0.1 M
Sodium chloride solution - strong electrolyte
⚡ HCl 0.01 M
Hydrochloric acid - strong acid, high conductivity
🧪 Acetic Acid 0.1 M
Weak acid - shows concentration dependence
🧬 KCl 0.05 M
Potassium chloride - reference electrolyte
⚗️ NaOH 0.2 M
Sodium hydroxide - strong base
📊 Resistivity to Conductivity
Convert resistivity to conductivity
🔋 Cell Constant Method
Calculate conductivity using cell constant
Calculate Conductivity
⚠️For educational and informational purposes only. Verify with a qualified professional.
🔬 Chemistry Facts
κ = 1/ρ. Units: S/m (siemens per meter).
— IUPAC
Λm = κ/c allows comparison across electrolytes.
— Electrochemistry
Kohlrausch: Λm = Λm° - K√c for weak electrolytes.
— Physical chem
Pure water: κ ≈ 0.055 µS/cm at 25°C.
— Water quality
What is Electrical Conductivity?
Electrical conductivity (κ) is a measure of a material's ability to conduct electric current. For electrolyte solutions, conductivity depends on the concentration and mobility of ions. It is the reciprocal of resistivity (ρ) and is measured in siemens per meter (S/m).
🔬 Key Concepts
Conductivity (κ)
The ability of a solution to conduct electricity. Measured in S/m. Higher values indicate better conductivity.
Resistivity (ρ)
The reciprocal of conductivity. Measured in Ω·m. Higher values indicate poorer conductivity.
Molar Conductivity (Λm)
Conductivity per unit concentration. Λm = κ/c, measured in S·m²/mol. Allows comparison of different electrolytes.
Limiting Molar Conductivity (Λm°)
The molar conductivity at infinite dilution. Represents maximum conductivity when all ions are independent.
How to Calculate Conductivity
Conductivity calculations depend on what information you have and what you want to determine.
📐 Calculation Methods
1. Conductivity from Resistivity
If you know the resistivity, calculate conductivity:
Where κ is conductivity (S/m) and ρ is resistivity (Ω·m)
2. Molar Conductivity
Calculate molar conductivity from conductivity and concentration:
Where Λm is molar conductivity (S·m²/mol) and c is concentration (mol/m³)
3. Kohlrausch's Law (Weak Electrolytes)
For weak electrolytes, molar conductivity depends on concentration:
Where Λm° is limiting molar conductivity and K is Kohlrausch constant
4. Cell Constant Method
Using conductivity cell with known cell constant:
Where K is cell constant (m⁻¹) and R is measured resistance (Ω)
When to Use Conductivity Calculations
Conductivity measurements are essential in many applications, from water quality testing to electrochemical analysis.
Water Quality
Monitor dissolved ion concentrations in water. High conductivity indicates high total dissolved solids (TDS).
- Drinking water testing
- Wastewater treatment
- Aquaculture monitoring
Analytical Chemistry
Determine electrolyte concentrations and study ion behavior. Essential for conductivity titration.
- Conductometric titration
- Ion concentration analysis
- Electrolyte strength determination
Electrochemistry
Study ion transport in electrochemical cells. Understand conductivity mechanisms in batteries and fuel cells.
- Battery electrolyte design
- Fuel cell optimization
- Ion transport studies
Conductivity Formulas
Basic Conductivity
Where: κ = conductivity (S/m), ρ = resistivity (Ω·m)
Molar Conductivity
Where: Λm = molar conductivity (S·m²/mol), κ = conductivity (S/m), c = concentration (mol/m³)
Kohlrausch's Law (Weak Electrolytes)
Where: Λm° = limiting molar conductivity, K = Kohlrausch constant, c = concentration (mol/m³)
Cell Constant Method
Where: K = cell constant (m⁻¹), R = resistance (Ω)
Degree of Dissociation (Weak Electrolytes)
Where: α = degree of dissociation, Λm = molar conductivity, Λm° = limiting molar conductivity
Strong vs Weak Electrolytes
Understanding the difference between strong and weak electrolytes is crucial for conductivity calculations.
Strong Electrolytes
- ✓Completely dissociate in solution (α ≈ 1)
- ✓Molar conductivity nearly constant with concentration
- ✓Examples: NaCl, HCl, NaOH, KNO₃
- ✓Λm ≈ Λm° (independent of concentration)
Weak Electrolytes
- ✓Partially dissociate in solution (α < 1)
- ✓Molar conductivity decreases with concentration
- ✓Examples: CH₃COOH, NH₃, H₂CO₃
- ✓Follow Kohlrausch's law: Λm = Λm° - K√c
📚 Official Data Sources
⚠️ Disclaimer: This calculator uses IUPAC conductivity definitions and electrochemistry standards. For precise work, consult IUPAC Gold Book and NIST for conductivity terminology. ASTM D1125 provides standardized water conductivity measurement procedures.