Good day,

Question

In relation to equilibrium, how would you know if an acid would spontaneously dissociate?

For example in this problem:
The equilibrium constant for the reaction HNO2(aq) + H2O(ℓ) → NO− 2 (aq) + H3O+(aq) is 4.3 × 10−4 at 25◦ C. Will nitrous acid spontaneously dissociate when [HNO2(aq)] = 0.15 M and [NO− 2 (aq)] = [H3O+(aq)] = 1.0 × 10−2 M?

Answer 1

Of course it will. The equilibrium constant tells you it will.
Keq = (products)/reactants = 4.3E-4. In order for there to be no dissociation it would be necessary for K to be zero and it isn't.

Answer 2

Ohh! Thank you, sir!