On the time scale of things, how long does it take for the CO2+H2O -> H2CO3 to be 50% towards equilibrium? I see the kintetic constants, but don't know how to use them since I have not dabbled in reaction kinetics yet since there was no need so far.

Are we talking seconds, minutes days or weeks here?

Kai

After an extended trip down memory lane and looking for books I no longer had, I constructed a scenario where I assumed that during carbonation it was possible to reach equilibrium for [CO2 aq] rapidly while the conversion to H2CO3 was negligible because that conversion to carbonic acid is "slow." The equation for carbonic aid is then according to my very rusty differential equations is then

[H2CO3] = k1/k2 [CO2 aq] x (1-exp(-k2t))

I'm not quite sure if I did everything correctly, but the form of the equation should be correct as the equation correctly predicts the equilibrium concentration of H2CO3 = k1/k2 [CO2 aq], with k1/k2 = the equilibrium constant and the form looks right from hazy recollection of reaction kinetics.

According to this equation, 50% of the equilibrium concentration of H2CO3 is achieved within 0.03 seconds.

I think if I did the derivation correctly and Wikipedia is correct that this pretty much blows my theory of the slow conversion of aqueous CO2 to carbonic acid as an explanation for achieving fine carbonation a few days after achieving gross carbonation away.

But I'm going to stick to my guns anyway. Some kind of acidification reaction takes a long time to occur because I've noticed in carbonating tap water that the water doesn't develop an acidic bite as quickly as gross carbonation is achieved.

Any ideas, Kai, mabrungard or others?