Why do buffers work

This is because they do not undergo any reactions that significantly alter their concentrations. In addition, HA and A - only rarely react with water. So, the weak acid and weak base remain in the solution with high concentrations since they only rarely react with the water. Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights.

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Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels. Facebook Facebook Twitter Twitter. Updated October 07, Featured Video. Cite this Article Format. When Sodium Fluoride dissolves in water, the reaction goes to completion, thus we obtain:. This buffering action can be seen in the titration curve of a buffer solution. As we can see, over the working range of the buffer.

Once the buffering capacity is exceeded the rate of pH change quickly jumps. This occurs because the conjugate acid or base has been depleted through neutralization. This principle implies that a larger amount of conjugate acid or base will have a greater buffering capacity. In this reaction, the conjugate acid, HF, will neutralize added amounts of base, OH - , and the equilibrium will again shift to the right, slightly increasing the concentration of F - in the solution and decreasing the amount of HF slightly.

Again, since most of the OH - is neutralized, little pH change will occur. Buffers function best when the pK a of the conjugate weak acid used is close to the desired working range of the buffer. This turns out to be the case when the concentrations of the conjugate acid and conjugate base are approximately equal within about a factor of For example, we know the K a for hydroflouric acid is 6.

For the weak base ammonia NH 3 , the value of K b is 1. It's always the pK a of the conjugate acid that determines the approximate pH for a buffer system, though this is dependent on the pK b of the conjugate base, obviously. When the desired pH of a buffer solution is near the pK a of the conjugate acid being used i.

In this example we will continue to use the hydrofluoric acid buffer. We will discuss the process for preparing a buffer of HF at a pH of 3. This is simply the ratio of the concentrations of conjugate base and conjugate acid we will need in our solution. How much Sodium Fluoride would we need to add in order to create a buffer at said pH 3.