Difference between H+ and H3O+

[Mao]

other case: H2O + H+ <--> H3O+ (altho you will hardly see these so it doesn't matter).

This does not happen. H+ and H2O cannot coexist due to the vast difference between their internal energy.

Sorry, take away the reverse sign.

H2O + H+ --> H3O+

Still not quite. H+ and H2O simply cannot coexist. In normal chemistry, H+ must always be bound to something, never by itself. This formulation is purely hypothetical.

[dc302]

My understanding is that this can be the intermediate step of a reaction no? After H+ has dissociated from something else, and before it has bound to H2O.

[Graphite]

I *think* acid transfer is a 1 step mechanism going from the acid to base.
The simplified notation might seem to show they H+ does dissociate first but I suppose that isn't a step shown in mechanisms

[dc302]

Oh well, I've forgotten most of first year chem anyway...

[samad]

Writing it in terms of H3O+ helps you understand Ka values and acid-base equilibria (Unit 4). The dissociation of an acid is more accurately a hydrolysis reaction,

eg. HCOOH + H₂O <--> HCOO^- + H₃O⁺.

the K value for this reaction is K= [H3O+][HCOO-]/[HCOOH][H2O], and the Ka is Ka= [H3O+][HCOO-]/[HCOOH]. (the concentration of water, which is constant, is multiplied out) if you wrote the reaction as a simple dissociation,

HCOOH <--> HCOO^- + H⁺,

your K value is the same as the Ka value. this doesn't allow you to understand how the Ka is derived

however, H+ and H3O+ are the same for the purpose of concentration.