How would you find a formula for a salt that contains NH4+ and is basic?

Question

I understand how to determine if a salt is acidic or basic but i don't know how you would go in reverse.

Answer 1

The (H^+) for a weak acid/weak base salt is (H^+) = sqrt (KwKa/Kb). So you look up a Ka that is smaller than Kb. You know Kb is about 1.8E-5 so any acid that is smaller than that should produce a basic solution. Look in your Ka tables for an acid smaller than 1.8E-5 and if the NH4^+ makes a stable salt with that you have your answer.