Buffer calculations


by n77ler
Tags: buffer, calculations
n77ler
n77ler is offline
#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 :)
Phys.Org News Partner Science news on Phys.org
NASA's space station Robonaut finally getting legs
Free the seed: OSSI nurtures growing plants without patent barriers
Going nuts? Turkey looks to pistachios to heat new eco-city
chemisttree
chemisttree is offline
#2
Feb27-08, 03:49 PM
Sci Advisor
HW Helper
PF Gold
chemisttree's Avatar
P: 3,725
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
n77ler is offline
#3
Feb28-08, 02:43 PM
P: 90
Sorry, they are both 0.10 M

chemisttree
chemisttree is offline
#4
Mar4-08, 11:24 AM
Sci Advisor
HW Helper
PF Gold
chemisttree's Avatar
P: 3,725

Buffer calculations


Review the Henderson-Hasselbach equation. Hint: pKa = -log[Ka]
lili moshi
lili moshi is offline
#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
Borek is online now
#6
Dec15-10, 07:11 AM
Admin
Borek's Avatar
P: 22,683
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)


Register to reply

Related Discussions
An Introduction to pH and Buffer Solutions Calculations Other Science Learning Materials 20
ph of (buffer + HCl) Biology, Chemistry & Other Homework 1
pH of buffer solution Biology, Chemistry & Other Homework 2
Buffer help. Chemistry 1
Tris- HCl buffer Biology 6