Buffer: Difference between revisions
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By definition a buffer is a substance (usually a weak acid and its conjugate base or a weak acid and its conjugate base)) which is added to a sample to avoid changes in its ph. A buffer must contain the chemical species for “neutralizing” added amounts of [[Acid|acid]] or [[Base|base]]. For example, if a buffer was a solution of a [[Weak acid|weak acid]] and its conjugate [[Base|base]] it would contain [[Acetic acid|acetic acid]] and [[Sodium acetate|sodium acetate]] or a [[Weak base|weak base]] and conjugate acid it would contain [[Ammonia|ammonia]] and [[Ammonium chloride|ammonium chloride]]. If there is a lot of acid or alkali added then the buffer will not be able to cope with such a change and will no longer able to maintain the pH. | |||
Buffers are most effective in the range [[PH]] = pK’a ± 1. Outside the range the [[Concentration|concentration]] of either the [[Acid|acid]] or the conjugate [[Base|base]] is too small to effectively resist the effect of added [[Hydrogen|hydrogen]] or [[ | Buffers are most effective in the range [[PH]] = pK’a ± 1. Outside the range the [[Concentration|concentration]] of either the [[Acid|acid]] or the conjugate [[Base|base]] is too small to effectively resist the effect of added [[Hydrogen|hydrogen]] or [[Hydroxide|hydroxide]] [[Ion|ions]].<br> | ||
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Revision as of 14:45, 21 October 2016
By definition a buffer is a substance (usually a weak acid and its conjugate base or a weak acid and its conjugate base)) which is added to a sample to avoid changes in its ph. A buffer must contain the chemical species for “neutralizing” added amounts of acid or base. For example, if a buffer was a solution of a weak acid and its conjugate base it would contain acetic acid and sodium acetate or a weak base and conjugate acid it would contain ammonia and ammonium chloride. If there is a lot of acid or alkali added then the buffer will not be able to cope with such a change and will no longer able to maintain the pH.
Buffers are most effective in the range PH = pK’a ± 1. Outside the range the concentration of either the acid or the conjugate base is too small to effectively resist the effect of added hydrogen or hydroxide ions.