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# How does a mixture of ${\mathrm{CH}}_{3}\mathrm{COOH}$ and ${\mathrm{CH}}_{3}\mathrm{COONa}$ act as a buffer when a small amount of $\mathrm{NaOH}$ is added?

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## Buffer solution:An aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa is known as a buffer solution.Its pH changes very little when a small amount of strong acid or base is added to it.A mixture of a weak acid and its salt with a strong base serves as an acidic buffer.$\underset{\mathrm{Acetic}\mathrm{acid}}{{\mathrm{CH}}_{3}\mathrm{COOH}\left(\mathrm{aq}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_{2}\mathrm{O}\left(\mathrm{l}\right)}â†’\underset{\mathrm{Acetate}\mathrm{ion}}{{\mathrm{CH}}_{3}{\mathrm{COO}}^{â€“}\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydronium}\mathrm{ion}}{{\mathrm{H}}_{3}{\mathrm{O}}^{+}\left(\mathrm{aq}\right)}$${\mathrm{CH}}_{3}\mathrm{COOH}$ is a weak acid, while ${\mathrm{CH}}_{3}{\mathrm{COO}}^{â€“}$ is a weak base.On adding $\mathrm{NaOH}$ to the system: $\underset{\mathrm{Acetic}\mathrm{acid}}{{\mathrm{CH}}_{3}\mathrm{COOH}\left(\mathrm{aq}\right)}+\underset{\mathrm{Sodium}\mathrm{hydroxide}}{\mathrm{NaOH}\left(\mathrm{aq}\right)}â†’\underset{\mathrm{Acetate}\mathrm{ion}}{{\mathrm{CH}}_{3}{\mathrm{COO}}^{â€“}\left(\mathrm{aq}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_{2}\mathrm{O}\left(\mathrm{l}\right)}+\underset{\mathrm{Sodium}\mathrm{ion}}{{\mathrm{Na}}^{+}\left(\mathrm{aq}\right)}$Since some of the acetic acids react with the ${\mathrm{OH}}^{â€“}$ from the base and convert it to water, the pH will not change as drastically.

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