Why does different condition decide what forms in a chemical reaction?

Hello! A curious Y12 student here

So in my AS chemistry class we were doing a topic on oxidation state. We had this homework where we had to state the oxidation number in some compounds - and 3 of them were different types of Sodium Chlorate. The teacher said one type of Sodium Chlorate (forgot which one exactly) forms at 70C or above.

I asked him why it is the case. He told me I don't have to know at this stage like every teacher always do. I guessed that the collision between particles increase at higher temperature causing bumping of Chlorine and Oxygen to increase as well and bonding more oxygen with chlorine - and asked him if this guess is right after class. But he told me it could be, and then said it's to do with mechanism and in chemistry different condition means different product. Obviously this answer didn't satisfy me and Mr Google also disappointed me, so here I am...

So why exactly does different temperature/concentration change what forms in a chemical reaction?

Thanks!


Posted from TSR Mobile

The more energy there is available the more types of bonds can get broken. This opens up the possibiity of other substances being formed that are more stable at the hgher temperature.

Hmm ok...
Thanks

Is there a name for this rule? So that I can google more (though I wouldn't understand much)

Posted from TSR Mobile

No, no rule, just common sense...

This is a very hard question to answer given where you are in your chemistry studies.
As you delve further into chemistry you will realise that what you have learnt previously is a simplification and there are explanations which without further study of entire topics in chemistry you don't yet know about.
The fact is there are many things which determine the feasibility of a chemical reaction and why sometimes a particular mechanism occurs and other times something completely different happens.
Well done for having an inquiring mind and asking questions. That is what a good scientist does but understand that there are times you will have to walk before you can run and with your limited knowledge and understanding of more advanced chemistry these questions can't be answered easily and certainly not on a forum with all its constaints.
Reaction feasibility is controlled by the likes of equilibrium law, redox potentials, entropy and free energy. Topics like these are completely unknown to you but form part of the A2 course and you will grasp them in due course and they will explain a lot.

Thank you for the response. Your response is much better than what I call the slamming door response from teachers :P

It seems as though you are talking Harry Potter language but it actually gave me more reasons to continue with chemistry beyond AS no matter how hard it may be!


Posted from TSR Mobile

One common way describing the different product formation under different conditions is kinetic vs thermodynamic control.

Considering the case of two possible products, one which is more stable (lower energy) but has a higher activation energy for the reaction pathway, and the other which is higher in energy but there is a smaller activation barrier.

Under kinetic control, typically lower reaction temperatures, the product formed is the one with the lowest activation energy pathway as there is not enough thermal energy to get the reactants over large activation barriers.

Under thermodynamic control, at high enough temperatures that there is sufficient thermal energy to get over all the relevant activation barriers, there will be a mixture of products dependent upon their relative thermodynamic stabilities.
The reaction will reach an equilibrium between the possible products, the majority product being the lowest energy molecule.