A buffer resists change in pH when a small amount of acid or base is added to it.

Quick Scoop

  • A buffer solution contains a weak acid and its conjugate base (or weak base and its conjugate acid).
  • It keeps pH almost constant when small amounts of strong acid or strong base are added, up to its buffering capacity.
  • If you add a large amount of acid or base, the buffer capacity is exceeded and the pH will change significantly.

So the filled-in sentence is:
“A buffer resists change in pH when small amount of acid or base is added to it.”

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