This one's nice, because you don't have to remember how many of this, combines with how many of that, because it's in the question. Whatever the negative charge on NO3 is, Na must have the same positive charge, because NaNO3 is in the question. And Fe must have three times that charge because there are three NO3 attached to the Fe. You need the number of NO3's to balance on both side of the equation so there will be : a) something + some* Fe(NO3)3 on one side and b) something + some** NaNO3 on the other side. And since there are three times as many NO3 in (a) as there are in (b), the number (**) needs to be three times bigger than (*) to balance it. So bearing in mind that you might have to multiply up later: a) something + Fe(NO3)3 b) something + 3 NaNO3 Now you can see you need to add in some Na in (a) and some Fe into (b) and you can see how many you'll need to balance with the other side. The only thing left is to determine whether (a) reacts to make (b) or the other way around. It's a fairly safe bet that in the right conditions, the reaction will go either way, so you could probably get some marks for writing it as an equilibrium reaction. To be absolutely sure, you have to do the experiment, or look up the result in a book, or look up the heat of dissociation or somesuch and balance the energy. But as a rough rule of thumb, the closer an ion is to the left and right edges of the perioidic table, the tighter it grabs hold. Sodium is right on the left edge of the table, so it's really not letting go of its NO3. The NaNO3 is therefore probably on the right hand side of the reaction as a product. Good luck with finishing the answer!