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posted by  blue8 on 4/27/2008 1:55:36 AM  |  status: Live  

please help.. due Sunday 5pm

Course Textbook Chapter Problem
General Chemistry N/A N/A N/A
Question Details:
A 25.0 mL sample of 0.150 M butanoic acid is titrated with a 0.150 M NaOH solution.  What is the pH before any based is added?  The Ka of butanoic acid is 1.5 x 10-5

a)  1.5x10-3
b)  4.82
c) 1.0x104
d)  2.83
e)  4.00
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posted by larios on 4/27/2008 2:16:18 AM  |  status: Live
Asker's Rating: Lifesaver   
blue8's comment:
"thank you"
Response Details:
Initial moles of HC4H7O2
 
 
     HC4H7O2 + H2O----- H3O + C4H7O2
I  0.00375mol    ----              0            0
C   -x                                    x             x
E 0.00375-x                         x              x
 
Ka= [H3O][C4H7O2] =       x2
            [HC4H7O2]         0.00375-x
 
1.5e-5= x2/ 0.00375-x        x=2.37e-4     pH=-log(2.37e-4) = 3.62 almost 4.0
 
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