[Saravanan]

The definition of spontaneous process states that "A spontaneous process is an irreversible process and maybe reversed by some external agency"
So can we say that all spontaneous reactions are irreversible reactions under the absence of some external force ?
Plz explain
Thanks in advance

[AdiDex]

See reversible process is just a hypothetical process..
There is no existence  Of reversible process .

So if you put external force or not ..it can't reverse the process...

[AdiDex]

so let me ask you one question ..so i can help you more....


If i have some water in a closed container ....i've boiled it ..it get evaporated ..then i condescend it again ..is this a reversible process or not..
Give your answer and Also elaborate it ..!!

[Saravanan]

I think it is reversible because the net amount of water remains the same and no water lost as it is a closed system . Am I right or wrong ?

[Arkcon]

I think it is reversible because the net amount of water remains the same and no water lost as it is a closed system . Am I right or wrong ?

All by itself, this statement isn't correct no.  Its incomplete, at the very least, because you've never described in this thread what reaction you're talking about.

[AdiDex]

So here is your answer..

Just think about this moment...you are reading this post , after reading this post you have a lots of possibilities to do something , you Can reply , you can drink some water , or you can go to sleep....aahhh there are just many many possibility..
And then by choosing one of them you will do another thing ...and there is also a lots of new possibilities .
So now you can think that there are endless possibilities...

So now the main point comes..

From trillions of trillions of trillions ( Aaahhh i can't write all of them ) possibilities , only one thing is going to happen..

So if you want to reverse the reaction you have to go exactly through that pathway...you have to 100% precise to reverse anything....which is practically impossible....(This is the same reason for that you can't travel to past )

So if you want to reverse the process you have to consider the surrounding also...
That why reversible process is just hypothetical process..
Yep the vapourisation and condensation is a reversible "change"..
But in terms of thermodynamics its an "irreversible  process" .

[AdiDex]

Same Explaination but in another way....

What is a Reversible Process?

The process in which the system and surroundings can be restored to the initial state from the final state without producing any changes in the thermodynamics properties of the universe is called a reversible process. In the figure below, let us suppose that the system has undergone a change from state A to state B. If the system can be restored from state B to state A, and there is no change in the universe, then the process is said to be a reversible process. The reversible process can be reversed completely and there is no trace left to show that the system had undergone thermodynamic change