What is buffer capacity

[reising1]

---

Members don't see this ad.

Question from EK 1001 Chem

838. Solution A contains a buffer formed of 2.0 M acetic acid and 0.8 M potassium acetate. Solution B contains a buffer formed of 0.2 M acetic acid and 0.08 M potassium acetate. How do the solutions compare?

Answer: The pH of solution A is the same as that of solution B, but solution A has a greater buffer capacity.

I understand that they have the same pH because 0.8/2.0 = 0.08/0.2, but what exactly is buffer capacity and why does solution A have more of it?

 

[Jepstein30]

Question from EK 1001 Chem

838. Solution A contains a buffer formed of 2.0 M acetic acid and 0.8 M potassium acetate. Solution B contains a buffer formed of 0.2 M acetic acid and 0.08 M potassium acetate. How do the solutions compare?

Answer: The pH of solution A is the same as that of solution B, but solution A has a greater buffer capacity.

I understand that they have the same pH because 0.8/2.0 = 0.08/0.2, but what exactly is buffer capacity and why does solution A have more of it?

Well there's more buffer in Solution A.. cause the concentration is higher. Thus, it can offset even more acid/base addition than Solution B. That's buffering capacity.. i.e. the ability to act as a buffer.

 

[PlumbLine]

Think about it this way, adding an equivalent amount of pure acid (or base), in terms of moles, to A and B will have very different results on pH. Does that make sense? Think about the different concentrations as you pointed out.