Is there a method for finding the net-ionic equation? I truly don't understand the method for finding the net-ionic equation for a reaction. It is not clear to me how you should decide what the products are, especially when there are multiple possibilities. 

Example:


  Excess potassium cyanide solution is added to aluminum bromide solution. 


The first thing that came to mind for the molecular equation is:

$\ce{3KCN\+AlBr3 \to 3KBr\+Al(CN)3}$

But apparently the correct molecular equation is:

$\ce{6KCN\+AlBr3 \to 3KBr\+Al(CN)6}$

I see no good reason why the one I thought of is incorrect. And to get the net ionic equation, the spectator ions are $\ce{K+}$ and $\ce{Br-}$. But why should I assume the solution is aqueous?

Another example:


  Chlorine gas is bubbled through dilute sodium hydroxide. 


Well its easy enough to get the reactants:

$\ce{Cl2\+NaOH \to ?}$

What first comes to mind is $\ce{Cl2\+2NaOH \to 2NaCl\+Cl2O\+H2}$

But the correct molecular equation is $\ce{Cl2\+2NaOH \to 2NaOCl\+NaCl\+H2O}$

What should be the thought process for arriving at the correct answer here. I am truly lost.

Another example:


  Lithium oxide reacts with sulfur dioxide. 


I recognize this as a synthesis reaction. However how can I predict if the product is lithium sulfite or lithium sulfate?
But apparently the correct molecular equation is $\ce{6KCN\+AlBr3 \to 3KBr\+Al(CN)6}$


That's not correct, what happenend to the other 3 potassium atoms?

It could form $\ce{Al2(CN)6}$ but you can't exclude $\ce{Al(CN)3}$ without further information beyond balancing of equations.

There are two main steps to balancing equation:


Balancing of each type of atom
Balancing number of electrons


If you've done both of those correctly, you've done all you can with balancing alone. 


  $\ce{Cl2\+2NaOH \to 2NaCl\+Cl2O\+H2}$


Above is clearly wrong because number of oxygen atoms doesn't balance


  $\ce{Cl2\+2NaOH \to 2NaOCl\+NaCl\+H2O}$


Above is clearly wrong because number of oxygen atoms doesn't balance