Kw

[Aishwarya Kosgi 1F]

Hi! I had a question about water and it's Kw value of 1x10^-14. Is water considered a strong acid/base? Since it is amphiprotic it can be an acid or a base, but since it has a Kw value, does that make it a weak acid/base? I remember Dr. Lavelle mentioning that only weak acids or bases have Ka values and I was wondering if this applies to water as well. Thanks!

[Akshata Kapadne 2K]

I believe water is both a weak acid and a weak base because it is amphiprotic and it does not ionize completely. So yes, I think you're right that its Kw value indicates that it is weak.

[SahajDole_1C]

It is considered as a weak acid and base.

[shevanti_kumar_1E]

Yes you are correct water can act as an acid and base because its amphiprotic. Pure water is both a weak acid and base. By itself water only forms a small number of H3O+ and OH- ions so it is considered a weak acid and base.

[Juwon Lim 2A]

To add on, pure water is neither acidic nor basic. The acid (H3O+) and base (OH-) exist mostly in similar concentrations, so we say water is neutral. However, water can both act as an acid and a base when molecules are in water because of its amphiprotic properties.

[Emerald Wong 1B]

Water can act as both an acid or a base, but it is weak because it does not ionize completely, so you are correct in your assumptions!

[Inderpal Singh 2L]

Since water does not ionize completely, it is considered both a weak acid and base.

If you would like a more in-depth description:

http://chemed.chem.purdue.edu/genchem/t ... nd%20bases.

[Adam Bustamante 1I]

water can be either an acid or a base and is considered weak because it does not completely ionize.

[Rob Tsai 2F]

Water can act as a weak acid or a weak base, but in terms of pH, it is neutral. The little amounts of H30+ and OH- it does contain is exclusively in equal amounts, so they cancel out. In terms of Ka values, a large Ka value indicates a strong acid, not just any Ka value. Hope this helps!