Question

I don't understand the hydrolysis of Zn(NO3)2: why will the solution be acidic?

Answer 1

Zn(NO3)2 + H2O --> Zn2+ + 2NO3-

Now,

Again these ions themselves will react with water because water is present here as a solvent.

Zn2+ + H2O --> Zn(OH)2 + H+

So, we see that Hydronium ions are remaining here in the solution

If we analyse for NO3-

No3- + H2O --> HNO3 + OH-

However, we know that Nitric acid is a strong acid and thus it'll again completely dissociate into H+ + NO3- again and H+ and OH- will again form H2O

This means that only the H+ ions from the reionization of Zn2+ ions remain in the solution and thus we can say that the solution will be acidic.