Jeff Rigby wrote:

Not that weak. If you take a distilled water and left it open pH goes
down from 7 to about 5.7 - just because of the presence of dissolved
carbon dioxide.

PH changes from 7, in other words from 5-9 in distilled water take very
little acid or base, in other words it's a very weak acid or base.

Remember that this change takes place in the presence of only about 380
ppmv of CO2 in the air. Increase amount of CO2 in the atmosphere and
the change will be higher. That doesn't mean carbonic acid is not a
weak one, you just don't need a strong acid to change pH when you have
solution close to pH 7.

Borek
--
http://www.chembuddy.com
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