[polly]

anyone know the answer to this problem?

given that the pka1 of carbonic acid is 6.10 and that the total carbon dioxide content(HCO3^-+CO2) of a blood sample of pH 7.48 is 0.00275M, calculate the concentrations of HCO3- and CO2 in the blood

this is what i know so far but not sure how to apply it

carbonic acid can undergo two dissociations in water:
H2CO3+H20--->HCO3^-+H3O⁺
HCO3^-+H2O--->CO3^-+H3O⁺

but because carbonic acid only ever exists in solution in equilibrium with carbon dioxide the following is written instead for the dissociation constant of carbonic acid (even though it looks like it should be the constant for carbon dioxide)

CO₂+H₂O<---->HCO3^-+H⁺ AND pKa = 6.10

now in order to solve this i thought maybe use the equation (and treat it as a buffer)

pH = pKa+log([base]/[acid]) ;
then insert the pH (given) and the pKa (given) ...then all that would be left is the two concentrations of [base] and [acid] ...and here lies the problem.

Which equation should i use? the first two equations don't have CO₂ in them.

If i use the last equation it certainly has CO₂ on one side and the HCO3^- on the other...but do I treat CO₂ as the acid and HCO3^- as the base?

I then probably solve [base]/[acid] = 0.00275M ? (somehow)

anybody that can assist is most appreciated
Thanks

[DevaDevil]

and your approach is?

[polly]

sorry...i edited it so that you can see what i was trying to do (if anything)

[polly]

The main problem I am having is which equation/s I should use in order to work out which is acid and which is base.

I am assuming I would use this one since it incorporates the CO2 and HCO3^- (both of which I need to work out the concentrations)

So is this even an acid base reaction?

CO2+H2O<---->HCO3-+H+ AND pKa = 6.10

Anybody with an idea?

[polly]

If it helps anybody else ...
i found a link to where the answer might be...I am still in the process of trying to understand it ...will let u know if I get the solution

http://www.chemistry.wustl.edu/~edudev/LabTutorials/Buffer/Buffer.html