[Borek]

Does that apply to all metal oxides, that the metal oxide is not a bronsted lowry base, only the oxide anion is. And the metal is a spectator ion?

No, metals are not always spectators.

Fe³⁺ + H₂O FeOH²⁺ + H⁺

Would you say the conjugate pairs are  O²⁻ / H2O

No, this is a two step reaction, so if anything there are two separate pairs of conjugate acid/base.

But in general: don't try to overgeneralize. There are several theories of acids and  bases, each one trying to be more general (check the wikipedia page on acid-base reactions). None of them is universal enough to cover everything, at the same time sometimes trying to squeeze every reaction into the same scheme is fruitless and doesn't produce any new insight, just confuses things.

[gavindor]

In reference to NaOH on the RHS of  the reaction

Na2O + H2O --> 2NaOH 

You say

NaOH neither Bronsted acid nor base. Na⁺ is just a spectator, it is OH^- that is reacting.

Would that apply also to Na2O  in Na2O + H2O,  since we don't get Na2OH?

And to CaO + H2O  since we don't get CaOH we get  Ca(OH)2 ?

I have heard that all arrhenius acids and bases, are bronsted lowry ones, but if we look at  an example like

HCl + KOH --> H2O + KCl

We don't get KOH2  So does that make KOH not a bronsted lowry base?  (And K+ a specatator ion?) So the base is just the OH- and not the KOH?

I can see that for NH3 + HCl --> NH4+ Cl-    There are no spectator ions. And you have easy to see conjugate pairs. Clear bronsted acids and bronsted bases.

Thanks

[Borek]

So does that make KOH not a bronsted lowry base?

Think in terms of net ionic reactions. All the time you ignore fact most of the substances involved are dissociated and you try to classify as bases or acids whole molecules. It doesn't work this way.

[gavindor]

Think in terms of net ionic reactions. All the time you ignore fact most of the substances involved are dissociated and you try to classify as bases or acids whole molecules. It doesn't work this way.

Would you say it does work in this case with no spectator ions?   NH3 + HCl --> NH4+ Cl-   


And based on what you've said about not considering whole molecules, would you agree that HCl + KOH --> H2O + KCl  has spectator ion K+ ?   I think even there, we would consider HCl as a whole, as the conjugate pair is HCl/Cl-  And we'd consider H2O as a whole because the conjugate pair there is OH-/H2O. But not KOH as a whole because K+ is a spectator ion. Would you agree?

[Borek]

HCl

You do know HCl is 100% dissociated in water solutions?

(Technically there exist some theoretical concentration of HCl, but it is completely negligible in the context of the reaction)

Sounds to me like you have learned earlier that KOH is a base and HCl is an acid, and you can't move ahead and understand it is only a simplification, one that at this moment (when learning about Bronsted acids/bases) doesn't matter any longer.

[gavindor]

HCl

You do know HCl is 100% dissociated in water solutions?

(Technically there exist some theoretical concentration of HCl, but it is completely negligible in the context of the reaction)

Sounds to me like you have learned earlier that KOH is a base and HCl is an acid, and you can't move ahead and understand it is only a simplification, one that at this moment (when learning about Bronsted acids/bases) doesn't matter any longer.

I do know that HCl dissociates and then reacts immediately. If it were HCl + H2O then we get H+(aq) + Cl-(aq) and the H+ is generally considered to be H3O+  and the Cl- just interacts with the H2O. 

And of course  in the examples, the HCl dissociates hence there's no HCl on the other side.

When you look at the conjugate pairs for NH3 + HCl --> NH4+ Cl-   what do you say they are -  I'd have thought they are HCl/Cl-  and NH3/NH4+ ?

I don't know if you're trying to get at the idea that the HCl dissociates therefore HCl isn't among the conjugate pairs.

I don't understand what you are getting at by pointing to the fact that HCl dissociates. I'm aware that it does

I'm fine with you saying HCl isn't a bronsted acid, and KOH isn't a bronsted base but i'm asking what the acid and base conjugate pairs are then?

[Borek]

I don't understand what you are getting at by pointing to the fact that HCl dissociates. I'm aware that it does

So start writing reaction equations as net ionic.

[gavindor]

I don't understand what you are getting at by pointing to the fact that HCl dissociates. I'm aware that it does

So start writing reaction equations as net ionic.

My issue there is  with the conjugate pairs I end up with..

HCl + KOH --> H2O + KCl

I suppose perhaps you don't like writing that HCl on the left because that's HCl(aq) and it's not explicitly stating that it's dissociated H+(aq) + Cl-(aq). And might suggest that it's not dissociated?  For me HCl(aq) means H+(aq) + Cl-(aq). Just as KOH(aq) means K+(aq) + OH-(aq).

OH- <-- fine that's not a spectator ion

H+ <-- that's not a spectator ion

K+ <-- that's definitely a spectator ion

Cl- <-- i'm not sure but I think it is a spectator ion..

H+ <-- not a spectator ion
--

H+ + OH- --> H2O

H+/BLANK,   OH-/H2O

If I take Cl- as a spectator ion then I get a blank. in one of my conjugate pairs. And that seems problematic?

When you write "Sounds to me like you have learned earlier that KOH is a base and HCl is an acid, and you can't move ahead and understand it is only a simplification, "    I am not sure if you are suggesting that K+ and Cl- are spectator ions. But if you are then, treating Cl- as such,  I get that issue of    H+/BLANK,   OH-/H2O

I am unsure how to identify spectator ions in bronsted  lowry  acid base reactions.

Normally with net ionic equations , as I understand it, one identifies spectator ions by them being those that don't change in oxidation state.

But in these bronsted lowry acid base reactions, at least in examples i've seen, none of the atoms change in oxidation state.  e.g.

H+ + OH- --> H2O  <-- H is +1.   O is 2-.  No change in oxidation state in any of the atoms there. But none of those are spectator ions. So it opens the question of how to identify spectator ions in bronsted lowry acid base reactions.

[Borek]

Think in terms of H₃O⁺.

In water there are no acids stronger than H₃O⁺ nor bases stronger than OH^-, it is called a levelling effect.

[Borek]

Normally with net ionic equations , as I understand it, one identifies spectator ions by them being those that don't change in oxidation state.

But in these bronsted lowry acid base reactions, at least in examples i've seen, none of the atoms change in oxidation state.  e.g.

You are freely mixing ions and atoms, as if they were the same thing. Don't.

Spectator is something that doesn't change and is written the same way before and after the reaction.

[gavindor]

okay i've looked into spectator ions again, and for ionic equations so granted, no neutral atoms..

first using this example AgNO3 + HCl --> HNO3 + AgCl(s)  and getting a net ionic equation from it.

Ag+(aq) + NO3-(aq) + H+(aq) Cl-(aq) --> H+(aq) + NO3-(aq) + AgCl(s)

I see oxidation states aren't relevant.. And there are no changes in oxidation states in this anyway..

The aqueous ions cancel. And we are left with this net ionic equation

Ag+(aq) + Cl-(aq) --> AgCl(s)

Ag and Cl are involved in a phase change, so aren't spectators.

The others are just aqueous ions on both the left hand side and right hand side, no phase change.. So are considered to be spectator ions and can be cancelled out.

The thing is though if I apply that to

Na2O + H2O --> 2NaCl

That's

Na2O(s) + H2O --> 2NaCl(aq)

So the Na+ is involved in a phase change, so it doesn't seem like a spectator ion. It's going from solid form, to  solvated ions.

[Borek]

Na2O(s) + H2O --> 2NaCl(aq)

NaCl?

Besides, the name IONIC implies you should write the product as dissociated on the RHS.

So the Na+ is involved in a phase change, so it doesn't seem like a spectator ion. It's going from solid form, to  solvated ions.

Yes.

Please don't hijack old threads to discuss a new subject, start a new thread to do so.

[gavindor]

well, when I wrote "Na2O(s) + H2O --> 2NaCl(aq)"  that was a typo at the end I meant Na2O(s) + H2O --> 2NaOH(aq)

and spectator ions there I don't think is a new subject 'cos eg you mentioned that Na+ is a spectator there in post #6..and it has been    but I take your point that you see it as a new subject and an old thread, so I will start a new thread re the spectator ions.

Thanks