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Buffer calculations

by n77ler
Tags: buffer, calculations
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n77ler
#1
Feb27-08, 03:19 PM
P: 90
1. The problem statement, all variables and given/known data
Buffer solution : CH_3COOH (55 mL) + CH_3COONa (45 mL)
Ka (CH_3COOH) = 1.76 x 10^-5

Calculate the expected pH of your buffer solution after it has been dilted by making 10 mL of buffer up to 100 mL with deionized water.

2. Relevant equations
Ice charts
n= c x v
c= n/v

3. The attempt at a solution
I've calculated the pH for other additions of strong acids and strong bases but I'm not sure how to start this one. Little bit confused... Just the first step would be a great help :)
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chemisttree
#2
Feb27-08, 03:49 PM
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You haven't given enough information to start. You need to know something about the concentrations of acetic acid (55 mL?) and acetate (45 mL?).
n77ler
#3
Feb28-08, 02:43 PM
P: 90
Sorry, they are both 0.10 M

chemisttree
#4
Mar4-08, 11:24 AM
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Buffer calculations

Review the Henderson-Hasselbach equation. Hint: pKa = -log[Ka]
lili moshi
#5
Dec15-10, 06:05 AM
P: 1
Quote Quote by n77ler View Post
1. The problem statement, all variables and given/known data
Buffer solution : CH_3COOH (55 mL) + CH_3COONa (45 mL)
Ka (CH_3COOH) = 1.76 x 10^-5

Calculate the expected pH of your buffer solution after it has been dilted by making 10 mL of buffer up to 100 mL with deionized water.

2. Relevant equations
Ice charts
n= c x v
c= n/v

3. The attempt at a solution
I've calculated the pH for other additions of strong acids and strong bases but I'm not sure how to start this one. Little bit confused... Just the first step would be a great help :)
the question is a little confusing due to the given volumes.i need help how to attempt the question.
Borek
#6
Dec15-10, 07:11 AM
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As chemisttree already wrote: use Henderson-Hasselbalch equation. Start calculating concentrations of both acid and conjugate base. At this stage it will be simple dilution problem.

(in fact you can solve the problem without calculating these concentrations, but I guess explaining the shorter route will only confuse you more)


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