How come the balanced equation for calcium oxide reaction with water is: CaO (s) +H2O (l) -- Ca(OH)2 (s) ? Shouldn't it be CaO(s) + H2O - Ca(OH) + H2O? Because of switching the innies and outies when we do the net ionic equation?

Question

How come the balanced equation for calcium oxide reaction with water is: CaO (s) +H2O (l) --> Ca(OH)2 (s) ? Shouldn't it be CaO(s) + H2O -> Ca(OH) + H2O? Because of switching the innies and outies when we do the net ionic equation?

kainui · Answer

It's CaO+H2O --> Ca(OH)2.

why? Count up all the calcium, oxygen and hydrogen on both sides. It has to be the same amount. It would be like if I put syrup on my pancake and then the result I got was syrup and bacon on top of my pancake when all I started with was the syrup and pancake separate.

also if that exists I want conservation of mass defying bacon making syrup.

anonymous · Answer

I thought we had to switch the cations and anions (innies and outies). If I switch it, can't I balance it from there too? I would balance it after switching.  How would I know if it doesn't switch just by looking at the equation and that it creates a combination product?  I odn't really understand that part. All the other equations I've been doing creates 2 products or H2 gas. Thanks!

kainui · Answer

Haha innies and outies, that's cute it's like they're belly buttons.

Can you show me an example of one you've done before so we can compare them together?

anonymous · Answer

Like say you are given Na3PO4 + CuSO4, then I would switch innies and outies to make 2Na3PO4 + 3CuSO4 -> 3Na2SO4 + Cu3(PO4)2? We don't do that with the example I posted? Thanks!

kainui · Answer

Ahh, I see. That's because this isn't an ion exchanging reaction, it's a synthesis reaction. Not all reactions involve switching partners, sometimes reactions can be two things joining together or two things breaking apart, and this is just one of those cases.

For instance if you have H2 and O2 gas and you combine them with a little heat, you get H2O and nothing else.

What you have to make sure of is that however much stuff you use still exists on both sides, whether it has a partner or not. So to balance those gases turning into water,

$$2H_2+O_2\rightarrow 2H_2O$$

I hope you believe that this is a reasonable example how we didn't swap innies and outies, we just stuck them together. But no matter what, it remained balanced.

anonymous · Answer

Thanks! Is there a way to tell if it is a synthesis reaction? I was just given the reactant side CaO + H2O ->?