Which buffer system is the best choice to create a buffer with
p...

Question

Which buffer system is the best choice to create a buffer with 
pH = 9.00? For the best system, calculate the ratio of the masses 
of the buffer components required to make the buffer. 
HF/KF HNO2/KNO2 
NH3/NH4Cl HClO/KClO

Accepted Answer

Hey, y'all. Let's get started on this next question. So if you need to prepare a buffer with a ph of 8.8, which one of the following acid and conjugate base pairs would you choose? So let's actually go through each of the following answer choices. So we have H. C. N. Which is our acid. My apologies, is an acid and we have K. C. N. Um where CN minuses are conjugate base, then we have HF or Hydrofluoric acid, where f minus is going to be our conjugate base. We have acetic acid where ch three C minus is going to be our conjugate base and then we have hydrogen. We have hcl Oh and so um here are cielo minus is going to be our conjugate base. Now let's actually recall our equation. So our ph is going to equal to the P. K. A. Plus the log of the conjugate base over the weak acid. And what we want to recall is that the best buffer is going to be the one that shows a P K. A value within Plus or -1 um of the ph So here we have a ph of 8.8. And so let's actually go through the p K. S. Of each of these answer choices. So the P K A. Of H C N is actually going to be 9.2 For Hydrofluoric acid. The PK. is going to be 3.46 For acetic acid. The PK. is going to be 4.75 and then for hcl oh minus, the p K is going to be 7.54. Now, out of all these answer choices, the one um acid and conjugate pair which has the value closest to the ph of our buffer, is going to actually be a, so A is going to be our final answer. Alright, everyone. I really hope this video helped and I will see you in the next one.

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