Electrolysis is used to break liquid water into hydrogen and oxygen gas. If I begin with 10 grams of liquid water, will the total mass of the two gases be greater than, less than, or equal to 10? Why?

Answer 1

Hello, Emily,

I'm tempted to write a balanced equation to help with this problem, but after reading what the question is, there is a straight-forward answer that is given by the Law of Conservation of Matter. It states that a chemical reaction will neither destroy nor create mass. The mass going in will be the same as the mass going out.

I had written a more detailed response to this yesterday, but I don't see it posted. Sorry if this is a repeat.

In my earlier response I note that the law does not necessarily apply to nuclear reactions. The energy involved with those reactions does come from converting a small amount of mass into energy, as per Einstein's E = mc²_. I ad also used a balanced equation to show an example of how 36 grams of H₂) does result in a total mass of O₂ and H₂ of 36 grams. Perhaps my response was too long.

I hope this helps,

Bob