Q-117. A buffer that is most effective at a pH of about 4.5 is
a) Acetate buffer
b) Bicarbonate buffer
c) Phosphate buffer
d) Tris buffer
Answer: Acetate buffer
Explanation:
The solution resists changes in pH most effectively at pH values close to the pKa.
A solution of a weak acid and its conjugate base, buffers most effectively in the pH range pKa ± 1.0 pH unit.
Acid———–pK
Acetic———pK = 4.76
Carbonic—–pK1=6.37and pK2=10.25
Phosphoric–pK1= 2.15, pK2=6.82 and pK3=12.38