# What happens to atoms that havent reacted in a chemical reaction?

So lets say that we have a chemical reaction with liquid oxygen and liquid hydrogen, but
weve got very little hydrogen, and very much oxygen. As we pour these two liquids together they react with on another and create water. However since there was a very much bigger amount of oxygen than hydrogen, there are still a lot of oxygen atoms left that have not reacted with the hydrogen, because there are no more free hydrogen atoms to react with.

Since pure oxygen is toxic, how do scientists avoid that some atoms do not react, also how do they calculate the amount needed for absolutely all atoms to react. What happens to the atoms that cannot react nor bond with anything, and lets say they are toxic and we were i.e. making water.
Thanks

Borek
Mentor
This is about stoichiometry and limiting reagents.

What happens to atoms that didn't react - nothing, they stay where they were, unchanged.

How do we ensure everything reacts - by taking stoichiometric amounts of reactants. Taking into account we can only measure amount with a limited precisions you can be sure some excess of one of the reactants will be left always.

No idea what you aim at with this toxicity talk. If you consider oxygen toxic (to some extent it is) just take excess hydrogen to be sure all oxygen was consumed in the reaction. Yes, you will be left with some excess hydrogen. See above.

Yeah but lets say for instance you needed to use some sort of alcohol like methanol and you needed to make it react with some element to create some product. And lets say that youre end product would result in a drinkeble product. I mean how would you avoid some of it being left over, it could make you blind.

Isnt hydrogen toxic as well?

Borek
Mentor
Yeah but lets say for instance you needed to use some sort of alcohol like methanol and you needed to make it react with some element to create some product. And lets say that youre end product would result in a drinkeble product. I mean how would you avoid some of it being left over, it could make you blind.

I already told you - you can use excess of another reagent.

In reality we purify the final product to get rid of everything we don't want, it is not like you are being given reaction mixture directly.

Isnt hydrogen toxic as well?

Everything is toxic.

I am afraid I dont get it. :(
Do you mind trying again?

Borek
Mentor
Do you know anything about stoichiometry?

Ygggdrasil