[mrdeadman]

In one sentence: If it can go the other way, ie. if I can get HCl gas out of hydrochloric acid, then it is an equilibrium.

that makes sense but aren't there more than one reaction taking place? not all of them are equilibrium. the vaporization is, but not the dissociation.

[Will]

In one sentence: If it can go the other way, ie. if I can get HCl gas out of hydrochloric acid, then it is an equilibrium.

that makes sense but aren't there more than one reaction taking place? not all of them are equilibrium. the vaporization is, but not the dissociation.

But by definition (I think) dissociation means that its reversible, otherwise it would be a hardcore chemical reaction happening (like hydrochloric acid and ammonia)!
I'm pretty sure you can only use the term dissociation for equilibriums.

[mrdeadman]

But by definition (I think) dissociation means that its reversible, otherwise it would be a hardcore chemical reaction happening (like hydrochloric acid and ammonia)!
I'm pretty sure you can only use the term dissociation for equilibriums.

sorry, but this is not true. since the acid is strong, it does not go from it's ions back to the undissociated acid, only weak acids do this which is why they are equilibrium which is why they have a dissociation constant Ka.

[Will]

sorry, but this is not true. since the acid is strong, it does not go from it's ions back to the undissociated acid, only weak acids do this which is why they are equilibrium which is why they have a dissociation constant Ka.

So you are telling me that hydrochloric acid can't fume HCl gas?

[Will]

sorry, but this is not true. since the acid is strong, it does not go from it's ions back to the undissociated acid, only weak acids do this which is why they are equilibrium which is why they have a dissociation constant Ka.

HCl has a K_a, but its just really big (thousands+?).

[mrdeadman]

So you are telling me that hydrochloric acid can't fume HCl gas?

no im telling you that HCl's dissociation is not an equilibrium reaction. dissociation and fuming are 2 different things.

sorry, but this is not true. since the acid is strong, it does not go from it's ions back to the undissociated acid, only weak acids do this which is why they are equilibrium which is why they have a dissociation constant Ka.

HCl has a K_a, but its just really big (thousands+?).

the reason it's so big is because HCl is a strong acid.

[Will]

The fuming occurs because it is an equilibrium, the HCl fumes were once originally H₃O⁺ and Cl^-.
Yes, I know the K_a is big because its a strong acid, but the fact it has a K_a means that its an equilibrium. K_a is an equilibrium constant which is just specific for acids.

I don't think theres anything more I can say to help you understand why its an equilibrium!
I'll just wait and see if some proper chemist like mike, Borek, mitch etc. can explain it better to you than I can.
I hope I've helped in one form or another...

[mrdeadman]

The fuming occurs because it is an equilibrium, the HCl fumes were once originally H₃O⁺ and Cl^-.
Yes, I know the K_a is big because its a strong acid, but the fact it has a K_a means that its an equilibrium. K_a is an equilibrium constant which is just specific for acids.

I don't think theres anything more I can say to help you understand why its an equilibrium!
I'll just wait and see if some proper chemist like mike, Borek, mitch etc. can explain it better to you than I can.
I hope I've helped in one form or another...

FUMING IS DIFFERENT THAN DISSOCIATION! the dissociation of HCl is not an equilibrium because it is a stong acid. Ka is ignored because HCl is a strong acid.

[Will]

FUMING IS DIFFERENT THAN DISSOCIATION! the dissociation of HCl is not an equilibrium because it is a stong acid. Ka is ignored because HCl is a strong acid.

lol, and there goes one of my scooby snacks.

[mrdeadman]

http://dictionary.reference.com/search?q=fuming
fuming:
To subject to or treat with fumes.
To give off in or as if in fumes.

v. intr.
To emit fumes.
To rise in fumes.
To feel or show resentment or vexation.
 dissociation:
Chemistry.
The process by which the action of a solvent or a change in physical condition, as in pressure or temperature, causes a molecule to split into simpler groups of atoms, single atoms, or ions.
The separation of an electrolyte into ions of opposite charge
http://dictionary.reference.com/search?q=dissociation

[mike]

HCl has a Ka, but its just really big

I think I would agree with this.

Maybe try reading Borek's chembuddy lecture notes, they are very useful for this type of discussion/argument

[rctrackstar2007]

But by definition (I think) dissociation means that its reversible, otherwise it would be a hardcore chemical reaction happening (like hydrochloric acid and ammonia)!
I'm pretty sure you can only use the term dissociation for equilibriums.

the thinking is wrong. dissociation is the amount that dissociates or separates. in no way does that define dissociation

[mike]

The majority of reactions could be considered reversible, even dissociations. Equilibrium is dynamic and equilibrium can be at either end of the scale (ie lots of product or lots of reactant). So an equilibrium with a strong acid would tend to favour the products of dissociation (with very little returning to the associated form).

[Will]

http://dictionary.reference.com/search?q=fuming
fuming:
To subject to or treat with fumes.
To give off in or as if in fumes.

v. intr.
To emit fumes.
To rise in fumes.
To feel or show resentment or vexation.
 dissociation:
Chemistry.
The process by which the action of a solvent or a change in physical condition, as in pressure or temperature, causes a molecule to split into simpler groups of atoms, single atoms, or ions.
The separation of an electrolyte into ions of opposite charge
http://dictionary.reference.com/search?q=dissociation

I think the last definition of fuming is a good one for me !
Could you explain to me where these fumes come from then if there is no equilibrium, and all the hydrochloric acid in my bottle is H₃O⁺ and Cl^- (which I agree with, but I disagree with you saying it can't go back to HCl and water)?

HCl has a Ka, but its just really big

I think I would agree with this.

Maybe try reading Borek's chembuddy lecture notes, they are very useful for this type of discussion/argument

lol, this is definately an argument.
To be honest I wish I never even bothered posting on this thread, all I wanted to do was make people understand chemistry better, not enter an argument that sees 3 of my yummy Scooby Snacks eaten!

[mrdeadman]

I think the last definition of fuming is a good one for me !
Could you explain to me where these fumes come from then if there is no equilibrium, and all the hydrochloric acid in my bottle is H₃O⁺ and Cl^- (which I agree with, but I disagree with you saying it can't go back to HCl and water)?

ok, i think i see what your saying now, but for the purposes of reactions and problems, HCl dissociation is not an equilibrium.