× Didn't find what you were looking for? Ask a question
Top Posters
Since Sunday
t
7
m
6
k
6
F
5
j
5
t
5
j
5
G
5
f
5
a
5
d
5
c
5
Home Q & A Board Science-Related Homework Help Chemistry (Moderator: Laser_3)
New Topic  
fishnchips fishnchips
wrote...
Posts: 37
Rep: 0 0
11 years ago
25.00 mL of a 0.12 M weak acid, HA, was titrated with 0.1 M NaOH. The pH of the solution was 4.2 after 10 mL of NaOH was added. What is the dissociation constant of the acid?
Read 402 times
2 Replies

Related Topics

Replies
wrote...
#1
11 years ago
You need to use the Henderson-Hasselbalch equation

pH = pKa + log([base]/[acid])

Calculate how much acid is left and how much salt is formed and put it in the equation

I get an answer of 4.5 for pKa
Ka = 3.16 x 10^-5
wrote...
#2
11 years ago
pH = pKa + log(A-/HA)

mmol HA at start = 3.0 (25 mL x 0.12 M)
Added NaOH = 1 mmol (10mL x 0.10 M)
[A-] = 1 mmol/vol
[HA] = 2 mmol/vol
log(1/2) = -0.30
pH = 4.2 = pKa + log(1/2)
pKa = 4.5 so Ka 3.2x10^-5
New Topic      
Quick Reply
Explore
Post your homework questions and get free online help from our incredible volunteers
  1021 People Browsing
Start New Topic Take the Tour CoursesNew Study Tools Topics Trending Browse by Textbook
Live Chat
Related Images
  
 257
  
 143
  
 157
Your Opinion
What percentage of nature vs. nurture dictates human intelligence?
Votes: 432
Previous poll results: Where do you get your textbooks?