[mnuslt]

How to you determine if SnCl2 or KNO for example is a acidic or a basic solution? without having to memorized all the strong and weak acids and bases.

[Borek]

There are areas in chemistry where memory is a key to succes

Sn is a heavy metal. Heavy metal hydroxides are not soluble (or weakly soluble at best, unless they are amphoteric). Hydrochloric acid is very strong. That's the key to proper answer.

KON - I suppose you meant KNO3. If so, both KOH and HNO3 are strong base/acid - and the solution will have similar properties as, say, NaCl. If it was KNO2 then HNO2 is a weak acid and you have exactly opposite situation when compered with the first question.