Hydrogen carbonate and phosphate buffers in the blood prevent excess hydrogen ions [H + ]…

Hydrogen carbonate and phosphate buffers in the blood prevent excess hydrogen ions [H⁺] produced by metabolic activity, from decreasing the pH of the blood. Carbon dioxide released into the blood during respiration is regulated by this system and prevented from causing changes in plasma pH prior to its excretion from the lungs. Excessive change in blood chemistry which would change the plasma pH from its normal level 7.4 . This excretes hydrogen ions and retains hydrogen carbonate ions and retains hydrogen ions if the pH rises. This may produce change in the pH of the urine from 4.5 to 8.5 . A fall in pH also stimulates the kidney cells to produce the base ion ammonia \(\left(\mathrm{NH}_{4}^{+}\right)\) which combines with acids brought to the kidney and is then excreted as ammonium salts.
 
Assuming that the buffer in blood is \(\mathrm{CO}_{2}-\mathrm{HCO}_{3}^{-}\) Calculate the ratio of conjugate base to acid necessary to maintain blood at its proper pH.
(K₁ of H₂CO₃ = 4.2 × 10^–7)