Acid-Base Equilibria

1. Jan 4, 2014

alingy1

Why is it that for the constant Kb, we always have to write H2O in the equation and we can omit H2O in acid reactions:

My textbook always writes:
NH3+H2O<=>NH4++OH-
NH4+<=>NH3+H+

Why can we not write NH3+H+<=>NH4+?

2. Jan 4, 2014

Staff: Mentor

We can. NH4+ is a weak acid, with a dissociation constant of 5.6×10-10, and above dissociation reaction is perfectly valid.

Your book my be sticking to one convention to make things easier to follow.

3. Jan 4, 2014

alingy1

Would the equilibrium constant be the same of that reaction? Or should we substitute OH- with Kw/H+?
Kw=10^-14

4. Jan 4, 2014

5. Jan 4, 2014

alingy1

I guess this means yes. :)