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Topic: Confused with Buffer Preparation  (Read 2615 times)

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Offline Boxxxed

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Confused with Buffer Preparation
« on: March 11, 2011, 06:34:06 PM »
I am calculating how many ml of 0.1 M CH3COOH is needed to make a buffer with a pH of 5.80

ph=5.80=4.75+log(base/acid)

11.22=base/acid

11.22(acid)=base

11.22(acid)=0.1M-acid

How did they go from the above step to this?

12.22(acid)=0.1M

They gave the acid a value of one and added it to both sides, Why?

Offline Borek

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Re: Confused with Buffer Preparation
« Reply #1 on: March 12, 2011, 04:43:27 AM »
I am calculating how many ml of 0.1 M CH3COOH is needed to make a buffer with a pH of 5.80

Is it a complete question? You need both acid and conjugate base, don't you?
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Offline Boxxxed

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Re: Confused with Buffer Preparation
« Reply #2 on: March 12, 2011, 10:06:02 AM »
Yes, I forgot to add. It asks for ml of both conjugate base and acid.

0.1 M of the conjugate base is given.

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Re: Confused with Buffer Preparation
« Reply #3 on: March 12, 2011, 02:00:33 PM »
I forgot to mention we are trying to create a 100 ml buffer.

5.80=4.75(base/acid)

11.22=base/acid

Total Moles of buffer = (0.1M)(0.1L) = 0.01 moles

0.01moles = 11.22(acid)+(acid)
0.01moles = 12.22(acid)
acid = 8.18x10-4 moles

The answer is 8.18x10-3

Figured it out.

8.18x10-4 moles divided by 0.1L = 8.18x10-3

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