Question

I'm trying to do this precipitation reaction problem, but I don't understand part of it.

The question is:
Does a precipitate form when aq. soultions of potassium nitrate (KNO3) and sodium iodide (NaI) are mixed?

Then it lists the solutions for the two:

KNO3(aq) --> K+(aq) + NO3-(aq)
NaI(aq) --> Na+(aq) + I- (aq)

I can't figure out how they got those charges. I thought since K is in group 1, it has a + charge, but I don't know how NO3 gets a negative charge.

Answer 1

Remember ALL compounds must have a zero charge (be neutral). Therefore, If K is +1 then NO3^- must be -1.
In H2SO4, H is +1 and that x 2 = +2; therefore SO4 must be 2-.