B What Does Svante Arrhenius' Salt Water Experiment Reveal About Entropy?

[Bernadette]

Hello

Sorry for my English...

We approach slowly (in a quasi-reversible way) an electrical charge of a glass of salt water.
Some ions arrange themselves in the glass.

What can we say about entropy of this transformation?

Bernadette

PS: My reflection comes from reading an old physics book (in French...) where an experiment by Svante Aarhenius, the "father" of ions, is described.

 

[berkeman]

Welcome to PF.

In the schoolwork forums and the technical forums, we require that you tell us what you think will happen. Can you show us the relevant equations that decsribe the Entropy of this setup, and tell us what you think will happen to the value of the Entropy? Thanks.

 

[Bernadette]

Hello

As it is showed on the picture, some ions (Cl- and K+) move.
In the sense of Boltmann's statistical physics, we have more order after approaching the charge.
I don't know the entropy variation equation for this transformation, if it exists.
I want to write that entropy decreases but I know it's impossible.

Bernadette

 

[berkeman]

I want to write that entropy decreases but I know it's impossible.

But is energy being added or subtracted from this system?

Also, is this for schoolwork? I can move your thread to the schoolwork forums if that is a better match...

 

[Bernadette]

Hello

We receive mechanical energy as electrical charges approach. So energy is subtracted from this (isolated) system.
It is not a schoolwork. Just asking questions in my mind. I am no more student, (regrets)

From the other side of Atlantic ocean.

Bernadette

 

[Bernadette]

Hello

No more response?

Can we say that when we apply the electric field (we approach the charge), the order increases?

Have a nice day

Bernadette