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I am new to chemistry and this website and while studying the production of sulphuric acid, I came across 'equilibrium reaction'. I also came across 'reversible reaction'. So, I want to know what is the difference between reversible reaction and equilibrium reaction.

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A Reversible reaction doesn't necessarily always happen. Sometimes it requires activation energy. A chemical equilibrium, is where a reversible reaction is occuring continuously equal on both sides.


It is important to note that it is not static. There is no extra net product on both sides, that is what makes it 'equal', but both reactions are continuously occuring.

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A real life example of an equilibrium is water.


In water (which is everywhere!), there are reactions going on all the time.


[ce] 2 H2O --> H3O+ + OH-[/ce]

and also the reverse reaction:

[ce] H3O+ + OH- --> 2 H2O [/ce]


These two reactions are "in equilibrium". It means that they are both equilly fast, and the net effect is that the [ce] H3O+ [/ce] and [ce] OH- [/ce] concentrations are not changing.


A reversible reaction is a reaction that can proceed in both ways. This means that equilibrium reactions are reversible.


A reversible reaction:

burning sugar (glucose). Your body is doing that all the time, but it will also work using a lighter :)

[ce] C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O [/ce]


Plants however are capable of the reverse reaction.

[ce] 6 CO2 + 6 H2O --> C6H12O6 + 6 O2 [/ce]

The "activation" they need comes from the sun. Plants need light.


the funny thing is that theoretically you could see the reaction where you burn sugar as an eqiulibrium... but the eqiulibrium lies all the way on the side of the CO2 and H2O... so the eqiulibrium constant is a HUGE number:


Constant = (product A concentration) * (product B concentration)/ ((reactant A concentration)*(reactant B concentration))

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another interesting reverse reaction, is that used in some glasses (spectacles) the sort that react to Light.


IIRC, it has something to do with copper oxide and a silver halide melted into the glass structure, upon Light exposure the halide is transfered to the copper, and when dark it switches back again.


but as you`ll see, all such reactions DO require the input of activation energy.

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Last time I checked all reactions were reversible; in some cases the equilibrium is very much to one side.


I agree... although that might not be very easy to understand. (The equilibrium constant being in the order of ten to the power... a lot, meaning that not a single molecule of the reactants remains, or not a single molecule of a product is formed).


Just a theoretical question, and perhaps not very chemical: is a nuclear reaction reversible?

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"is a nuclear reaction reversible?"

I believe so, but the temperatures requierd are a bit awkward to deal with. Do you have a tame supernova in your lab?

Well said :)


Fission is certainly reversible, the reverse process is called fusion. But, as John mentioned, you'd require a tame star in your lab.

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