chemistry
posted by Mima .
carbon dioxide dissolves in water to form carbonic acid. Estimate the thermodynamic equilibrium constanst (K) for this reaction (delta Gf values: H2CO3=  616.1, H2O=  237.1, CO2=  394.4) .
Carbonic acid then ionizes in water (Ka1= 4.5 x 10^7). Ignoring Ka2, estimate (K) for the overall process by which CO2 and H2O form H and HCO3.
What is the pressure of CO2 in equilibrium with carbonated water at 25 C and PH= 4.78?

CO2 + H2O ==> H2CO3
dGrxn = (dG products)  (dG reactants)
Then dG = RTlnK
Solve for K.
Then H2CO3 ==> H^+ + HCO3^
k1 = 4.5E7
For the two reactions together you have
CO2 + H2O ==>H^+ + HCO3^ and Keq = k1K.
Finally, convert pH 4.78 to H^+, substitute into the equation (HCO3^ = H^+ too) and solve for partial pressure of CO2. 
Thank you so much for replying, but I can't understand how to solve for partial pressure of CO2, when I get the [H^+] from PH then how to solve for partial pressure of CO2?

Thanks a lot, I got it.

I kept record of all IP addresses and they will be reported to UCI undergrad offices.

@Amanda lolololol

@Amanda, k

Thanks!

I still don't understand how to find the partial pressure of CO2. I've got the H+ concentration but I'm stuck at that step.

the partial pressure is determine by
K= [hc03][h]/pressure 
So the pressure =.202 atm

where do you get the T in the first one?

I don't understand how to find the partial pressure can someone explain it to me please I have a homework due tonight that is similar to this