A buffer is prepared by adding 0.95 mol of
acetic acid CH3COOH and 4.25 mol of sodium
acetate NaCH3COO to enough water to make
a 5.0 L solution. What is the pH of the
buffer? The ionization constant for acetic
acid is 1.8 × 10−5
CH3COOH <======> H+ + CH3COO-
Initial 0.19M 0 0.85M
Change -x +x +x
Equilibirum 0.19 - x x 0.85 +x
1.8e-5 = (0.85x+x^2) / (0.19 -x)
3.41e-6 -1.8e-5x = 0.85x + x^2
0 = x^2 + 0.849982 - 3.41e-6
x = 0.0000040118307272
pH = - log(0.0000040118307272)
pH = 5.4
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