PLEASE SHOW ALL WORK. I DID THIS QUESTION MULTIPLE TIMES, AND I DONT KNOW WHAT I
ID: 955119 • Letter: P
Question
PLEASE SHOW ALL WORK. I DID THIS QUESTION MULTIPLE TIMES, AND I DONT KNOW WHAT I DID WRONG.
The following information is given. Concentration of sodium acetate: 1.071M Concentration of Acetic Acid is: 1.041M The pKa of acetic acid is 4.75.
a) Calculate the pH of the stock acetic solution.
b) Calculate the pH of the stock sodium acetate solution.
The above values are called theoritical values. The values recorded within the experiment using pH meter was pH of stock acetic acid = 2.35 and ph of sodium acetate is 8.38.
Thanks
Explanation / Answer
pKa = 4.74
a)
HA <-> H+ and A-
Ka = [H+][A-]/[HA]
Ka = 10^-4.75
[H+]= x= [A-]
[HA] = M-x = 1.041-x
10^-4.75 = (x*x)/(1.041-x)
x = h+ = 0.0043
pH = -log(H) = -log(0.0043) = 2.36653
b)
for the conjugate
A- + H2O <-> HA + OH-
Kb = [HA][OH-]/[A-]
Kb = Kw/Ka = 10^(14-4.75) = 5.55*10^-10
[HA]= [OH-]= x
[A-] = 1.071 -x
Kb = [HA][OH-]/[A-]
5.55*10^-10 = (x*x)/(1.071 -x)
x =) OH = 2.43*10^-5
pO H= -log( 2.43*10^-5) = 4.6143
pH = 14-4.6143 = 9.3857