How to Calculate Buffer Capacity
What is Buffer Capacity?
Buffer capacity (β) measures how much acid or base a buffer solution can absorb before the pH changes significantly. It depends on the total concentration of the buffer and is maximum when [HA] = [A⁻] (i.e., pH = pKa).
Step-by-Step Guide
- 1β = 2.303 × Ca × Cb / (Ca + Cb)
- 2Ca = acid concentration · Cb = base concentration
- 3Maximum when Ca = Cb (equal concentrations)
- 4Higher total buffer concentration → higher capacity
Worked Examples
Input
0.1M acetic acid + 0.1M sodium acetate
Result
β = 2.303 × 0.1 × 0.1 / 0.2 = 0.115 mol/L
Maximum buffer capacity for these concentrations
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