aqua_chem
Aquarium Advice Addict
Does it lower ph at high ph levels? As per chart towards bottom of link. Kind of confused here.
I'm guessing the HC03(-) goes to ---> H(+) + C03(--) but don't really understand why if you wouldn't mind explaining? Or any links (need to be simple though as haven't done chemistry in a very long time). Any help here much appreciated.
Carbon Dioxide and Carbonic Acid
Ask and you shall receive!
It's all because of these equation from that site:
H2CO3 (aq) <-> H+ (aq) + HCO3- (aq)
Equilibrium expression:
turns into:
Because H2CO3 (carbonic acid) rapidly decomposes into CO2 and H2O at room temp and pressure...
And this principle: Le Chatelier's Principle.
If I suddenly add a bunch of bicarbonate (HCO3-), then the system must 'adjust' to make that equation true (ie, Q > K). It does this by reacting with a hydrogen atom, consuming it to make CO2 and H2O, and thus making the system more basic. So there is in the end less HCO3- and less H+, more CO2 is made, and nobody cares about water. The equation is then balanced again (Q = K).
The reaction in the other direction:
HCO3- (aq) <-> H+ (aq) + CO32- (aq)
doesn't happen much at pH below about 8 because CO3-- is a much stronger base than HCO3-, and as such will not yield it's proton until the entire solution is much more basic.
BIG FAT EDIT: I see your question. I misspoke and will edit my post as such. It increase pH, decreases acidity. You are correct. But I made this big post and deleting it would make me sad.