Question

How do I get the molecular formula for Iron(II) nitrate + barium chloride-->

Answer 1

Fe(NO3)2 + BaCl2

Answer 2

I'm guessing you mean what happens when you mix aqueous solutions of these two compounds, and the answer is that since both are ionic and soluble in water they will dissolve into their respective cations and anions, namely Fe+2, NO3-, Ba+2, Cl-.

At this point, you might wonder whether a precipitation reaction might occur, but it does not, because the other two combinations of cation and anion -- FeCl2 and Ba(NO3)2 -- are both soluble. So nothing at all happens.