Answer to Question #42665 in Other Chemistry for Austeja
In 10 mL of blood sample pH was 7,56. A high amount of acid was added into the blood. After that volume of CO2 in a sample was 6,13mL. pKa is 6,1. Find concentrations of CO2 and HCO3- in blood.
Please, help me, I almost understand how everything should be calculated, but somewhere I keep thinking faulty I guess because can't get the possible answers anyhow...
Find the amount of substance of CO2. Assume that the volume was measured at ambient conditions (298.15 K, 100 kPa). n(CO2) = pV/RT = 2.473*10-4 mol Assume that the only substance responsible for blood pH is CO2. Carbon dioxide dissociates in water according to the following equation: CO2 + H2O --> H+ + HCO3- We have a buffer system, and its pH can be calculated from the following equation: pH = pKa + lg [A-]/[HA] where [A-] is the concentration of bicarbonate ion HCO3-, and [HA] is the concentration of free CO2. [A-]/[HA] = 10^(pH - pKa) = 28.84 The total amount of CO2 and HCO3- in the solution is equal to the amount of evolved CO2. Therefore we can find the total concentration of these particles: c(CO2 + HCO3-) = n(CO2)/V(solution) = 2.473*10-4/0.01 = 0.02473 mol/L Let x denote the concentration of free CO2 in the solution. Hence the concentration of HCO3- ions is 28.84x x + 28.84x = 0.02473 x = 8.29*10-4 mol/L 28.84x = 2.39*10-2 mol/L