Question

23. Alkalosis is a condition in which the body fluids have excess base (alkali). This is the opposite of excess acid (acidosiss). If a patient has a blood pH= 7.6 and [CO2]= 1.2 mM, what is the [HCO3-] in the patient’s blood? The pKa of HCO3- = 6.1.

Answer 1

The process can be written as

CO₂ + 2H₂O --------------------> HCO₃^- + H₃O⁺

Now the Henderson-Hasselbalch Equation can be written for the above equilibrium as

pH = pKa + log[HCO₃^-/CO2] .......................(1)

Given to us,

pH = 7.6

pKa = 6.1

[CO2] = 1.2 mM

now put these values in equation (1), we will get

7.6 = 6.1 + log[HCO₃^-/1.2 mM]

==> log[HCO₃^-/1.2 mM] = 1.5

==> [HCO₃^-/1.2 mM] = 101.5

==>  [HCO₃^-/1.2 mM] = 31.6

==> [HCO₃^-] = 31.6 x 1.2 mM

==>  [HCO₃^-] = 47.4 mM Answer

Hence, the concentration of [ HCO₃^-] in the blood = 47.4 mM

Thank you