Carbonic acid, H2CO3, is a weak diprotic acid formed in rainwater as it passes through the atmosphere and dissolves carbon dioxide. Write chemical equations for the Equilibria involved in the stepwise ionization of H2CO3 in water.

Answer: H2CO3(aq) -- H+ + HCO3- or H2CO3(aq) + H2O -- H3O+ + HCO3-

HCO3- -- H+ + CO3^-2 or HCO3- + H2O -- H3O+ + CO3^-2

can someone please explain the second line of the answer to me?

Question

Carbonic acid, H2CO3, is a weak diprotic acid formed in rainwater as it passes through the atmosphere and dissolves carbon dioxide. Write chemical equations for the Equilibria involved in the stepwise ionization of H2CO3 in water.

Answer: H2CO3(aq)  --> H+ + HCO3- or H2CO3(aq) + H2O --> H3O+ + HCO3-

HCO3-  --> H+ + CO3^-2 or HCO3- + H2O --> H3O+ + CO3^-2

can someone please explain the second line of the answer to me?

aaronq · Answer

what is it that you don't understand? another H+ is coming off, leaving the CO3 with a -2 charge

anonymous · Answer

so it ionizes twice?

aaronq · Answer

yes, its a "di"protic acid

di = 2
protic from proton i.e. H+

aaronq · Answer

just like H2SO4, or the triprotic acid H3PO4

anonymous · Answer

so then the prefix represents the number of times it ionizes right?

aaronq · Answer

yep, although i'm not sure ionizes would be the correct term for sequential dissociations, since they're already ions the first time.

anonymous · Answer

yeah, okay, i get it now. thanks (:

aaronq · Answer

ok cool (Y)