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Topic: How can an acid not be an acid??? huh???  (Read 5366 times)

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bugsmenot

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How can an acid not be an acid??? huh???
« on: August 23, 2006, 05:34:06 AM »
I am studying the reaction between acid and magnesium at A level.

As far as i was previously aware, the reaction is like this:

Mg(s) + 2H+(aq) ? Mg2+ (aq) + H2(g)

with the H+ coming from the acid.

the acid in this case is HCl so i would assume this is happening to get the H+:

HCl --> H+   +   Cl-

However, the acid is diluted so apparantly, this occurs instead:

H2O(l) + HC l(g) --> H3O+ (aq) + Cl-(aq)


If this is the case, then what is the reaction between this d :-Xiluted acid and magnesium??

is a H+ involved?? what happens to this hydroxonium ion??

Offline Albert

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Re: How can an acid not be an acid??? huh???
« Reply #1 on: August 23, 2006, 05:40:39 AM »
Do you think there is any difference between H+(aq) and H3O+(aq)?

bugsmenot

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Re: How can an acid not be an acid??? huh???
« Reply #2 on: August 23, 2006, 05:47:00 AM »
...im probably being really stupid.

does the H3O then dissotiate to form another H+ and water?

Offline xiankai

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Re: How can an acid not be an acid??? huh???
« Reply #3 on: August 23, 2006, 07:02:00 AM »
H+ is a theoretical ion, because its a free proton, which is WAYYYY too reactive and does not really exist for any appreciable time when it is in a environment with lots of mean water molecules waiting to collide with it.

therefore when acids dissociate in water, H+ is produced, but it quickly attaches itself to a water molecule forming H3O+.

but when writing reactions, it does not really matter whether u write  H+ or H3O+, because for balancing purposes, you cancel the water on both sides of the equation:

H3O+ + OH- --> 2H2O

more or less the same as

H+ + OH- --> H2O

this is to say, the water molecule that the proton is attached to does not react or anything, but is a spectator molecule.
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Offline Borek

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Re: How can an acid not be an acid??? huh???
« Reply #4 on: August 23, 2006, 07:23:54 AM »
H+ is a theoretical ion, because its a free proton, which is WAYYYY too reactive and does not really exist for any appreciable time when it is in a environment with lots of mean water molecules waiting to collide with it.

Note that H3O+ is probably kind of simplification too, as IIRC experimental evidence shows that ions present in the solution are more complicated - something like H5O2+ or H7O3+ or even H9O4+...
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bugsmenot

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Re: How can an acid not be an acid??? huh???
« Reply #5 on: August 23, 2006, 07:32:39 AM »
excelnt thats c leared thiings up thanks a lot guys

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