Question

identify the precipitate if any that forms when KOH and Cu(NO3)2 are mixed

Answer 1

You know right away that KOH will dissociate into K+ and OH- because K is in group I and so always dissolves. You also know Cu(NO3)2 will dissociate into CU(2+) and 2 NO3- because NO3-containing compounds always dissolve as well. This eliminates KNO3 as being a precipitate, because K and NO3 always stay dissolved.

That means we need to look at Cu(OH)2 as being a possible precipitate. If you have a list of solubility rules, you'll see that all OH containing compounds are insoluble, except those containing group I elements or some group II elements. Cu isn't in group I or group II, which means Cu(OH)2 will be insoluble and so will precipitate!

Hope that helps!