× Didn't find what you were looking for? Ask a question
Top Posters
Since Sunday
T
3
s
3
o
3
G
3
k
3
C
3
a
3
K
3
f
3
j
3
b
3
c
3
Home Q & A Board Science-Related Homework Help Chemistry (Moderator: Laser_3)
New Topic  
nylande nylande
wrote...
Posts: 14
Rep: 1 0
11 years ago
What concentration of ammonia, [NH3], should be present in a solution with [NH4+] = 0.809 M  to produce a buffer solution with pH = 9.59? For NH3, Kb = 1.8E-5.
Read 332 times
2 Replies

Related Topics

Replies
wrote...
#1
11 years ago
pH = pKa + log (base/acid)
wrote...
#2
11 years ago
Using the Henderson-Hasselbalch Equation:
pH = pKa + log (base/acid)
pH = pKa + log ([NH3]/[NH4+])

Kb(NH3) x Ka(NH4+) = Kw
1.8 x 10^-5 x Ka(NH4+) = 1.0 x 10^-14
Ka(NH4+) = 1.0 x 10^-14 / 1.8 x 10^-5 = 5.56 x 10^-10
pKa = - log Ka = - log (5.56 x 10^-10) = 9.26

pH = pKa + log ([NH3]/[NH4+])
9.59 = 9.26 + log ([NH3] / 0.809)
0.33 = log ([NH3] / 0.809)
0.33 = log [NH3] - log 0.809
0.33 = log [NH3] + 0.09
log [NH3] = 0.33 - 0.09 = 0.24
[NH3] = 10^0.24 = 1.74 M
New Topic      
Quick Reply
Explore
Post your homework questions and get free online help from our incredible volunteers
  997 People Browsing
Start New Topic Take the Tour CoursesNew Study Tools Topics Trending Browse by Textbook
Live Chat
Related Images
  
 227
  
 201
  
 293
Your Opinion
What's your favorite coffee beverage?
Votes: 302
Previous poll results: Do you believe in global warming?