A CLOSER LOOK
The pH of blood is maintained within a small range (slightly above 7) by a bicarbonate buffer
system.Consider a buffer solution of acetic acid and sodium acetate:
CH 3 COOH H+ + CH 3 COO−When a small amount of NaOH is added to the buffer, the OH− ions from the NaOH react with the H+
ions present in the solution; subsequently, more acetic acid dissociates (equilibrium shifts to the
right), restoring the [H+]. Thus, an increase in [OH−] does not appreciably change pH. Likewise, when
a small amount of HCl is added to the buffer, H+ ions from the HCl react with the acetate ions to
form acetic acid. Thus [H+] is kept relatively constant and the pH of the solution is relatively
unchanged.