Buffers and their functions

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Buffers and their functions

Postby 704578485 » Tue Nov 24, 2015 11:15 am

After lecture yesterday, I understand that the main purpose of a buffer is to maintain the ph of a certain solution. I realize that this is essential for human life and biology because the ph of blood must be maintained very carefully and soil ph must stay relatively constant for plant life to grow. I just am having trouble grasping what is happening with solutions and buffers on a molecular level. In the course reader the functioning of a buffer is illustrated by the chemical formula of a weak acid reacting with water to form its conjugate base and hyrdonium ions. The thing I don't grasp is, is that whole equation considered the buffer or is it just that weak acid. Also, if the weak acid is considered the buffer how do you go about adding it to a solution to maintain its ph? Lastly, why does adding a salt to a weak acid make it a stronger buffer?

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Re: Buffers and their functions

Postby Chem_Mod » Tue Nov 24, 2015 11:51 am

A weak acid by itself is not a buffer. A buffer must consist of a weak acid AND its conjugate base. or, it can consist of a weak base AND its conjugate acid. The best buffer is created when you mix the two components in equal mole amounts.

For example: if you have both a weak acid and its conjugate base in equal amounts:
If you add HCl to the buffer, the conjugate base will eat up the extra protons, removing them from solution, and the pH will not change.
If you add NaOH to the buffer, the weak acid will neutralize all the extra OH in solution by donating its H to it, creating H2O, and the pH will not change.

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