[Carboxyluke]

So, I am a high school student and I'm a little more involved with Chemistry than my fellow classmates you kind of have a... Hate towards it. I've learned all sorts of things like aromatics, carboxylic acids, acids and bases and how they work and so much more on my own. But something I just simply have so much trouble understanding, that is so simple...

Why do reactions even occur?

Yeah, I know, so simple right? It may seem to have a simple answer, but I want so much more detail needs to be invested in this answer. A simple reaction that you just completely understand is Na + Cl. No duh! Electron donor and taker! That's easy! But that's not the kind of reactions I mean. I mean reactions that involve things like NaOH + CaBr₂.

I ended up learning that these substances can react when put into a solvent, most of time I'm pretty sure it's going to be water. They then disassociate and become electrolytes which then can react, their cations and anions switching. That makes perfect sense. But how can things like HCl, an extremely strong acid, dissolve and react with things without that solvent? The H can't disassociate into H⁺ and it therefor can't react, right? So how does it even react? It doesn't make much sense to me.

Thanks for answers,
Carboxyluke

[billnotgatez]

I did a GOOGLE on

Why do chemical reactions occur

and got a multitude of hits

By the way
If you have not read the forum rules please do so
The link is near the top middle of most all pages in the forum.

[Irlanur]

I don't think that a Google search will do at all, and I don't understand the harsh answer of billnotgatez. I think your question goes into the very essence of what chemistry is about, and a Forum won't help you very much. Maybe not even a University degree on its own. I would like to encourage you to keep asking. Just be aware that the more answers you get, the more questions you will have. Simple questions are usually the hardest to answer.

A simple reaction that you just completely understand is Na + Cl. No duh! Electron donor and taker! That's easy!

Is it? so what happens exactly? how do we know?

[P]

But how can things like HCl, an extremely strong acid, dissolve and react with things without that solvent? The H can't disassociate into H⁺ and it therefor can't react, right? So how does it even react? It doesn't make much sense to me.

Thanks for answers,
Carboxyluke

With the acid I guess you could say the solvent (or the medium for the reaction) is water? The reactions only take place on the surfaces of solids in the acid as this is where the molecules physically meet...  as the solid dissolves or reacts into the acid it is being dissolved...  the acid itself is the solvent in a way.

A solvent isn't strictly necessary. Two solids can react. They will react at the surfaces where they touch only...  if they are powdered then there will be more of a reaction when the powders are mixed due to more surface area of each substance being able to come into contact with the surfaces of other powdered particles. In solution you have all of the molecules from each solid free to move about in the solution, which gives much easier access for the reactants to come into physical contact with each other.

Why do reactions even occur?

With ALL reactions, chemical or physical, it is all about finding the most energetically stable arrangement for the molecules and atoms involved.

I answered in short - you could go into so much more detail - you could write a book about the subject even.

[P]

PS - As I said - you could write a book on it.  At Uni I took a 10 week lecture course that purely focused on gas phase reactions alone. Then you have reaction between solid/solid, solid/liquid, gas/liquid, liquid/liquid, then you have reaction in solutions and also reactions that only take place on a surface of a catalyst...  in all cases the reaction takes place to reduce the energy of a system and to produce the most energetically stable state for the system.

[Corribus]

You can go down this endless path of "why, why, why" the universe is the way it is. "Thermodynamics" may seem like a trite way to answer, but ultimately it's true. Any system approaches the lowest energy available to it unless work is applied. Ultimately that's why reactions happen. We can drive reactions in the opposite way by moving energy from one place to another, but even the application of work results in energy cost somewhere else. You might then be encouraged to ask why does the universe approach a state of maximum energy dispersal? I guess that's a question for theoretical physicists and maybe even philosophers to ponder. It's been suggested that even gravity has entropic underpinnings.

I mean, how fundamental do you want to go? At some point, every level of understanding is based on the acceptance of something as being axiomatic. The position of that something tends to shift downward as you progress through your education and it also depends on where on the scientific spectrum you position yourself (physics < chemistry < biology, etc.). At some point, the details just get too unimportant to be practically bothered by. I.e., at some level quantum mechanics probably makes a difference to neurology, but do you really need to understand quantum mechanics to study the practical origins of, say, Parkinson's disease? Yet it certainly is more relevant to designing a better laser.

Anyway, I nevertheless applaud the interest in understanding the mechanics of the world around you. 

[Babcock_Hall]

An old but interesting book is E. L. King's How Chemical Reactions Occur.  It is pitched at the level of college freshman chemistry and is more focused on kinetics and mechanism (how) than it is on why reactions occur.

[Enthalpy]

"finding the most energetically stable arrangement" would need subtle analysis. For instance, it is not "minimize the internal energy". As a counter-example, many dissolutions happen despite they absorb heat.