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How to use pH calculator

Acid-base titration is a quantitative analytical technique used to determine the concentration of an unknown acid or base by reacting it with a solution of known concentration. A pH indicator (such as phenolphthalein) or a pH meter is often used to detect the equivalence point, where the acid and base completely neutralize each other.

Key Points

  • Titration is based on the neutralization reaction between an acid and a base.
  • The equivalence point is reached when moles of acid = moles of base.
  • The titration formula helps calculate unknown concentrations.

Formula & Equation Used

The calculator uses the following equations:

pH = − log 10 ( [ H + ] )

For weak acids, the hydrogen ion concentration [H⁺] is approximated by:

[ H + ] = K a ⋅ C

Where:

  • pH: acidity of the solution
  • [H⁺]: hydrogen ion concentration (mol/L)
  • Ka: acid dissociation constant
  • C: concentration of the acid (mol/L)

For strong acids, which dissociate completely, the pH is:

pH = − log 10 ( C )

Example Problem & Step-by-Step Solution

Problem:

Calculate the pH of a 0.1 M acetic acid (CH₃COOH) solution. The Ka of acetic acid is 1.8 × 10-5.

Solution:

  1. Identify the concentration C=0.1 M and Ka=1.8×10−5.
  2. Calculate the hydrogen ion concentration using Ka⋅C:
[H+]=1.8×10−5×0.1=1.8×10−6=1.34×10-3
  1. Calculate pH:
pH = − log 10 ( 1.34 \times 10^{-3} ) = 2.87

Thus, the pH of the 0.1 M acetic acid solution is approximately 2.87.