Kb Calculator
Calculate Kb from equilibrium concentrations of a weak base, or find the pOH and pH of a weak base solution given its Kb and initial concentration.
Use the Kb Calculator
For the reaction B + H₂O ⇌ BH⁺ + OH⁻, enter equilibrium concentrations:
Enter Kb and the initial base concentration to solve for equilibrium pH:
Enter values and click Calculate to see results.
Kb
Equilibrium Details
Expression Used
Summary
The Kb Calculator determines the base dissociation constant (Kb) for a weak base given the equilibrium concentrations of the base, its conjugate acid, and hydroxide ions. It also works in reverse: enter Kb and the initial base concentration to calculate the equilibrium pOH and pH of the solution. All calculations use the exact quadratic formula for maximum accuracy.
How it works
- Choose a calculation mode: "Find Kb" or "Find pH from Kb".
- In Find Kb mode, enter the equilibrium concentrations of [OH⁻], [BH⁺], and [B].
- In Find pH mode, enter the Kb value and the initial base concentration (C).
- Click Calculate to see Kb (or pH), pOH, pKb, percent ionization, and the full equilibrium expression.
- Use the Copy button to transfer the primary result to the clipboard.
Use cases
- Determine Kb of ammonia, methylamine, or any weak base from lab measurements.
- Predict the pH of an ammonia or amine solution given its Kb.
- Verify equilibrium constant calculations for general chemistry homework.
- Compare base strengths by computing Kb for different bases.
- Support analytical chemistry titration analysis and buffer design.
- Study acid-base equilibria in biochemistry and pharmacology.
- Convert between Kb and pKb for reference or reporting.
- Check percent ionization to confirm whether the weak-base approximation is valid.