How Does a Buffer Solution Work?

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Buffer solutions are chemical mixes that resist changes in pH, and when strong acids or strong bases are introduced, they're able to react with it to absorb the solution. Learn about the rise or fall of pH levels in buffer solutions with help from a science teacher and field biologist in this free video on chemistry.

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Video Transcript

Hi, I'm Brian with Ericksontutoring.blogspot.com. Today we're going to discuss how a buffer solution works. So, buffers are chemical mixes that resist changes in pH. The way that they do that is, they're essentially a mixture of a conjugate acid and a, or a weak acid and a weak base. And so when you add a small amount of either a strong acid or a strong base, it's able to react with it and essentially absorb that addition. So if you add a strong acid, the weak base interacts with it and forms a weak acid, which just slightly changes the pH. And in turn, if you add a strong base, then your weak acid will interact with it, forming a weak base and change the pH a small amount in the other direction. Blood is a good example of a buffer that we all know. So we'll look at acetic acid, a buffer, and see how it interacts with a strong base and a strong acid. So we have acetic acid here, I've abbreviated it to save us time and confusion reading a long molecule. It's essentially hydrogen and then acetate. So as I've shown it, it's a weak acid that breaks up into hydrogen ions and acetate, negative ions. So, since it's a buffer, it should be able to absorb the small addition of either a strong acid or a strong base. So if we add HCl, which is a strong acid, we'll increase the amount of hydrogen ions that are in the solution because the HCl contributes those hydrogen ions. What that's going to is it's going to force some of the reverse reaction to occur more to help balance out the overall equation. Basically, if you increase how much hydrogen's here, we're going to push it backwards, and the end result is that we form more acetic acid, which is a weak acid, and only slightly lower our pH. In turn, if we add a weak, or a strong base, so something like sodium hydroxide, NaOH, the hydroxyl is going to interact with the weak acid, which is acetic acid, and it's going to push our reaction forward, forming additional water, so the hydrogen reacts with the OH, and we also form some acetate, which is slightly negatively charged and a weak base. So, we add a tiny bit of weak, or we end up increasing the amount of weak base, which slightly increases our pH. So, we have explored, very briefly, how buffer solutions work.

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