Why does Kw increase acidity?

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reburbia

Full Member
7+ Year Member
If Kw=(H)(OH)
Then why does an increase in Kw necessarily mean that the water is getting more acidic (more H) and not more basic (more OH)?

For some context, I'm looking at a EK passage where higher temps increase the Kw. A Kw of 2.92E-14 produces a pH of 6.7

pm1

Full Member
If Kw=(H)(OH)
Then why does an increase in Kw necessarily mean that the water is getting more acidic (more H) and not more basic (more OH)?

For some context, I'm looking at a EK passage where higher temps increase the Kw. A Kw of 2.92E-14 produces a pH of 6.7

The formation of water is an exothermic process heat is considered a product.
Then, if you add heat the reaction will shift to the left, increasing both H+ and OH-. I would think that Kw would increase along with [H+] and [OH-], the reaction would still be neutral but it would change the pH of neutral water (would be lower).

Somebody please correct if I'm wrong.

chiddler

Full Member
10+ Year Member
if you increase Kw, then the product of H*OH must increase. Therefore concentrations of both species are increasing.

Definition of acidity: pH = -log[H]. There is more H, therefore it is more acidic.

But wait there's more!

pOH = -log[OH]. There is more OH, therefore it is also more basic.

I mean if you have pure water and the H+ concentration is increasing, it has to come from somewhere, right? It must be from the H2O's dissociating their hydrogen.

MrNeuro

Full Member
7+ Year Member
The formation of water is an exothermic process heat is considered a product.
Then, if you add heat the reaction will shift to the left, increasing both H+ and OH-. I would think that Kw would increase along with [H+] and [OH-], the reaction would still be neutral but it would change the pH of neutral water (would be lower).

Somebody please correct if I'm wrong.

Yeah but pOH + pH DOES NOT= 14