Posted by Kaleen on .
Calculate [CO32 ] in a 0.019 M solution of CO2 in water (H2CO3). If all the CO32 in this solution comes from the reaction shown below, what percentage of the H+ ions in the solution is a result of the dissociation of HCO3‾?
HCO3‾(aq) H+(aq) + CO32(aq)

Chemistry 
DrBob222,
........H2CO3 > H^+ + HCO3^
initial.0.019....0........0
change...x.......x.......x
equil.0.019x.....x........x
k1 = (H^+)(HXO3^)/(H2CO3).
Substitute into k1 expression and solve for H^+. I obtained approximately 1E4 but you should do it more accurately.
Then HCO3^ ==> H^+ + CO32^2
init.1E4.......0.......0
change.x.......x.......x
equil...1E04x...x.......x
I have show the two above as if the H^+ from equation 1 is not the same as in equation 2. Actually, they are the same for both equation; however, I have done it this way to show the different.
k2 = (H^+)(CO3^2)/(HCO3^2)
But from equation 1 we see that (H^+) = (HCO3^), which makes from equation 2 that (C03^2) = k2 = about 5E11
So what percentage of the H^+ comes from k2? Very small.
[(H^+)from k2/(H^+)from k1]*100 =% from the second ionization.