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Dr. T Presents:. The Henderson-Hasselbalch Equation. For more, please visit: http://www.ChemistryWithDrT.com/. The Henderson-Hasselbalch Equation. What is it? Used to quickly calculate the pH of a buffer solution.

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Dr t presents

Dr. T Presents:

The Henderson-Hasselbalch Equation

For more, please visit: http://www.ChemistryWithDrT.com/


The henderson hasselbalch equation

The Henderson-Hasselbalch Equation

  • What is it?

    • Used to quickly calculate the pH of a buffer solution.

      • Buffer: A solution containing a weak conjugate acid-base pair that is able to accommodate the addition of strong acids and bases without the pH of the solution changing much.

    • It is based on some underlying assumptions (later in video).

    • Advantage: The concentrations of the buffer components can be used directly rather than using an ICE chart (always write the chemical equation).

    • Derivation: Can be found in your textbook or class lectures.


The henderson hasselbalch equation1

The Henderson-Hasselbalch Equation

  • What is it used for?

    • Used to quickly calculate the pH of a buffer solution.

      • Biologists – Buffers for cell growth media

      • Biochemists – Buffers for enzyme kinetics assays

      • Chemists – Buffers for pH sensitive chemical reactions

      • Students – Buffers for laboratory experiments


The henderson hasselbalch equation2

The Henderson-Hasselbalch Equation

  • How is it used?

  • Problem:

    • 0.20 mol of benzoic acid and 0.10 mol of sodium benzoate are dissolved in 1 L pure water. What is the pH of this solution?

      • Given: Ka of benzoic acid = 6.3 x 10-5


The henderson hasselbalch equation3

The Henderson-Hasselbalch Equation

0.20 mol of benzoic acid and 0.10 mol of sodium benzoate are dissolved in 1 L pure water. What is the pH of this solution?

Given: Given: Ka of benzoic acid = 6.3 x 10-5


Tips tricks

Tips & Tricks

  • Assumption made by the Henderson-Hasselbalch Equation:

    • The amount of acid that ionizes in solution is negligible compared to the amount of acid and conjugate base that are used to form the buffer.

  • What it means for you:

    • The Henderson-Hasselbalch equation is inappropriate to calculate the pH of a solution containing only a strong acid or a strong base.

    • Be sure that the amount of acid and conjugate base added are at least 102 larger than the Ka.


Tips tricks1

Tips & Tricks

  • pH and Buffer Capacity

    • The pH of the buffer solution is determined by the Ka of the conjugate acid.

    • The amount of acid or base that can be added to the system and neutralized by the buffer before the pH changes by a significant amount depends on the amount of conjugate acid and conjugate base used to make the buffer. (Buffer capacity)

    • For example:

      • A solution of 1 M benzoic acid and 1 M sodium benzoate has the same pH of a solution containing 0.1 M benzoic acid and 0.1 M sodium benzoate. The 1 M solution has a larger buffer capacity, and can therefore neutralize a greater amount of added acid or base.


Dr t presents

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For more resources, please visit: http://www.ChemistryWithDrT.com/


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