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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Nekee123 on July 09, 2021, 01:02:35 AM

Title: Henderson-Hasselbach
Post by: Nekee123 on July 09, 2021, 01:02:35 AM: Hello,

I need help with a question. Its okay if I don't get the answer I just need *delete me*!

So I have 71 mL of Acetic Acid and 1.059 g of Sodium Acetate. The concentration of the acetic acid is 0.01 M. I have to find the pH of the buffer solution. I know that I have to use the Henderson-Hasselbalch equation but I don’t know how to use it. It just look like a foreign language! I know that the unknown is the pH but I don't know if the concentration of the conjugate base is 0.01 or if that is the concentration of the weak acid. But then, I feel like I am missing a concentration somewhere and I literally don’t know where to begin.
Title: Re: Henderson-Hasselbach
Post by: Nekee123 on July 09, 2021, 01:06:19 AM: Ok so now I know that acetic acid is the acid so it’s concentration is the weak acid. Then the concentration of the conjugate base should be the sodium acetate. The pKa is 4.76. I found those! But now how do I find the pH if I am missing the conjugate base concentration?
Title: Re: Henderson-Hasselbach
Post by: Orcio_87 on July 09, 2021, 01:33:07 AM: What is the problem ? Concentration of acetic acid is known and sodium acetate = 1,059 g / 71 ml.
Title: Re: Henderson-Hasselbach
Post by: Nekee123 on July 09, 2021, 03:24:06 AM: Ok then the pka that I should use is 4.76??? Its the correct one? I am no longer sure.
Title: Re: Henderson-Hasselbach
Post by: Borek on July 09, 2021, 04:11:47 AM: Quote from: Nekee123 on July 09, 2021, 03:24:06 AM
Ok then the pka that I should use is 4.76??? Its the correct one?

Yes, that's the pKa of the acetic acid.

Quote
I am no longer sure.

Why? What makes you doubt it is the right one?
Title: Re: Henderson-Hasselbach
Post by: Nekee123 on July 09, 2021, 09:36:34 PM: Because I don’t know how to find the concentration of the sodium acetate.
Title: Re: Henderson-Hasselbach
Post by: Nekee123 on July 09, 2021, 09:58:25 PM: Ok nevermind !!! I finally found what was the problem!! I had the wrong concentration. But thanks to anybody that tried to help me!