Acid-Base Titration Calculator
Finding an Unknown by Watching a Reaction Complete
Titration turns a chemical reaction into a measuring instrument. By adding a solution of known concentration until the reaction with an unknown sample is exactly complete — the equivalence point — the volume used becomes the key to calculating whatever was unknown at the start, whether that's a concentration or a volume.
The Formula
This relationship holds at the equivalence point for a monoprotic acid reacting with a monobasic base in a 1:1 ratio. Ca and Va describe the acid; Cb and Vb describe the base. Given any three values, the fourth is determined.
Where This Calculation Matters
- Standardizing a solution — titrating against a known standard is how a lab determines the exact concentration of a freshly made reagent.
- Quality control assays — acid-base titration is a standard method for verifying the concentration of vinegar, antacids, and other consumer products.
- Water hardness and alkalinity testing — environmental labs titrate water samples to determine acid-neutralizing capacity.
- Teaching quantitative analysis — titration is typically the first hands-on technique used to connect volume measurements to concentration.
A Worked Example
Titrating 25.00 mL of an unknown HCl solution requires 22.50 mL of 0.100 mol/L NaOH to reach the equivalence point:
How to Use This Calculator
- Choose which quantity to solve for — Ca, Va, Cb, or Vb.
- Fill in the three known values among Ca – Concentration of Acid (mol/L), Va – Volume of Acid (L), Cb – Concentration of Base (mol/L), and Vb – Volume of Base (L).
- Select Calculate to solve for the missing quantity at the equivalence point.
Related Calculations
Working with a buffer near the equivalence point instead of a sharp endpoint? The Henderson-Hasselbalch Calculator covers that regime. To convert the resulting concentration into pH, use the pH Calculator.