Buffer solutions are solutions that resist changes in pH on addition of an acid or a base.
Buffer solutions are made from a mixture of
The amount of acid and base are roughly in equal concentrations.
The hydrogen carbonate buffer (H2CO3/ HCO3-) is an example of a natural buffer.
It keeps the pH of blood relatively constant around 7.4.
The buffer is made from the weak acid H2CO3(aq) and its conjugate base, the hydrogen carbonate ion, HCO3-(aq).
If the pH of blood falls outside the range of 6.8 to 7.8 death occurs.
Excess acid in the blood is neutralised by the hydrogen carbonate ion
H+ (aq) + HCO3-(aq) ← → H2CO3(aq)
Excess base in the blood is neutralised by carbonic acid
H2CO3(aq) + OH-(aq) ← → HCO3-(aq) + H2O(l)
The levels of the carbonic acid in the blood are monitored by the brain which controls the rate of breathing.
H2O(l) + CO2(g) ← → H2CO3(aq)