Exam season is here! I've been working through a lot of practice questions in preparation. I'm very confused as to how my professor reached the answer to this question:
c. Given that the pH of your blood has not changed, the blood sample at that time was
actually a mixture of CO2 and HCO3-. From the information in a and b, calculate the
concentrations of CO2 and HCO3-.
Basically someone measured the pH of their blood to be 7.35, and after strenuous exercise the pH was still 7.35
The information from part A and B:
A: K3 of the reactions: CO2 + H20 <--> H2CO3 <--> HCO3 + H+ is equal to 4.2x10-7.
K1 = -1.7x10-3
K2 = -2.5x10-4
Which of course makes pK3 6.37
From a blood sample of exactly 10 ml, 5.6 ml (2.5x10-4 mols) of CO2 were extracted.
And this is where I get lost. I have attached a picture of the correct answer, but the working out is not complete. Where did the 9/1 come from? And how does that mean that the concentration of HCO3 is 0.024M? Likewise with CO2, (1/10)(0.025 M) =0.0025 ?? I don't understand where these numbers are coming from.
Also if anyone has any tips or methods that would help me understand and use the Henderson-Hasselbach equation, I'd love to hear it.
I have attached a picture of my previous attempts, which is pretty much just me flapping around not really knowing what to do, just so that you know I have tried.
Cheers in advance!