Water as Acid or Base

[Labiba Sardar 2A]

When H2O is a reactant in an acid-base reaction, how do you know whether it will act as an acid or base? Do you first look at the other reactant and determine whether that other reactant will be an acid/base?

[Junxi Feng 3B]

I think the best way is to first look at the product and determine which reactant receives protons (the chemical formula is usually given). For example, H2O + CO2=H2CO3, in this case, we look at the product, which is H2CO3, meaning the CO2 accepts protons from H2O. Therefore, water acts as an acid because it donates protons(hydrogen) to CO2.

[philipraj_1F]

It can be either so it would depend on what the product and other reactant are meaning how it changes.