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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: nchristedem on February 20, 2009, 11:36:43 AM

Title: Is desorption the of LiBr a physical or chemical phenomenon?
Post by: nchristedem on February 20, 2009, 11:36:43 AM

Consider this reaction:
AB + heat <=> A + B.

AB = low concentration solution of LiBr
A = high concentration solution of LiBr
B = water( vapour)

The forward reaction is called desorption. As it is only the concentration which change after the reaction, can you say that it is a chemical reaction?
We wonder wether it is a physical phenomenaon.

Title: Re: Is desorption the of LiBr a physical or chemical phenomenon?
Post by: nj_bartel on February 20, 2009, 12:55:08 PM

Can you define the difference between a physical and chemical process?

Title: Re: Is desorption the of LiBr a physical or chemical phenomenon?
Post by: nchristedem on February 21, 2009, 01:51:41 AM

Quote from: nj_bartel on February 20, 2009, 12:55:08 PM

Can you define the difference between a physical and chemical process?

I think that in chemical processes, final elements (products) are differents from former elements (reactives). In physical phenomena, the chemicl nature of elements before and after the reaction is the same.

Title: Re: Is desorption the of LiBr a physical or chemical phenomenon?
Post by: nj_bartel on February 21, 2009, 03:46:24 AM

Ok, but you need to be more specific, or at least more clear.  You say that in a chemical process, the products are different from the reactants.  Would you say that chopping coarse sugar up into powdered sugar constitutes a chemical reaction?  Why or why not?  What is the difference between the reactant and the product?  What are they made of?

Title: Re: Is desorption the of LiBr a physical or chemical phenomenon?
Post by: nchristedem on February 21, 2009, 04:19:39 AM

Quote from: nj_bartel on February 21, 2009, 03:46:24 AM

Ok, but you need to be more specific, or at least more clear.  You say that in a chemical process, the products are different from the reactants.  Would you say that chopping coarse sugar up into powdered sugar constitutes a chemical reaction?  Why or why not?  What is the difference between the reactant and the product?  What are they made of?

I don't know excatly what is "Chopping coarse sugar up into powdered sugar" (I am not english people). but if i put for example sugar in tea, it is not a chemical reaction since the sugar doesn't react with elements in the tea.
The difference is about the chemical links.

Title: Re: Is desorption the of LiBr a physical or chemical phenomenon?
Post by: nj_bartel on February 21, 2009, 11:28:31 AM

Oh sorry, I didn't realize - you speak good English  :P  You are correct - dissolving sugar in tea is not a chemical reaction.  Notice that you said this without noting the amount of sugar going into the tea.  So obviously it doesn't matter whether the tea has 10 grams of sugar per liter tea, or 10 grams of sugar per half liter tea.