ionic equations (1 Viewer)

[marsenal]

If you're asked to write a net ionic equation for the reaction between an acid and a base, what ions would you exclude?
What I am referring is something like:
(i) potassium oxide and sulfuric acid
(ii) barium hydroxide solution and nitric acid.

 

[spice girl]

*** exclude all soluble ions.

i.e. the ions that are soluble in both before and after reaction

(i) potassium oxide and sulfuric acid
exclude K and SO4_2- because they are soluble in both cases.

2H+ + O_2- -> H2O(l)

here I highly suspect K2O is in solid form, because oxides exist in water as hydroxides. in that case, it becomes:
K2O(s) + 2H+ -> 2K+ + H2O(l)

(ii) barium hydroxide solution and nitric acid.
exclude Ba, NO3-
so OH- + H+ -> H2O

 

[abdooooo!!!]

yep, spice girl is right.

just remember that in a net ionic equation you are only asked to show the actual ionic species that undergoes change in the reaction.

the ions Ba_2+ and NO3- is the spectator ion because they do not undergo chemical change in the equation, they remain with the same charges before and after the reaction.

while the ions H+ and OH- undergos chemical change to become a covalent neutral specie in the form of H2O, therefore it needs to be shown in the net ionic reaction.

 

[mannnnndy]

Another thing, if the ion stays in the same state before & after the reaction, such as (aq), then it means that it is a spectator ion. If it undergoes a change of state then it is not a spectator ion.

 

[marsenal]

I guess that means I've also got to learn my solubility rules. Never was a fan of them.
Thanks.

 

[Twintip]

So when they ask for an 'ionic equation' in the HSC, they really mean just a 'net ionic equation'? My teacher has said this to me from day one, but I have never fully believed him even though he is an HSC marker because all the text books include spectator ions in a lot of their ionic equations.

 

[mannnnndy]

When they ask for a full ionic equation, they want you to show all the ions, including spectator ions.
When they ask for a net ionic equation, they dont want spectator ions, just the ones that participate in the reaction.

 

[abdooooo!!!]

but sometimes the questions just says write an ionic equation, never stating what form of ionic equation it should be. i once wrote a full ionic equation for a question that just says "ionic equation"; my teacher mark it wrong... so i think markers only want the simplest form of equations when they don't state specifically.

 

[marsenal]

What about when you have a reaction between a weak acid and a weak base, and you want to write the net ionic equation.
The example I'm thinking of is,
NH3 + CH3COOH --> NH4+ + CH3COO-

So in this case would there be no difference between the net and the full ionic equations? Or would you neen to add like H2O in the full one?

 

[abdooooo!!!]

Originally posted by marsenal
NH3 + CH3COOH --> NH4+ + CH3COO-

So in this case would there be no difference between the net and the full ionic equations? Or would you neen to add like H2O in the full one?

there is a difference. you don't need to include CH3COO- in an net ionic equation because nothing has happened to it, its the same before and after the reaction. for the full ionic equation you have to show the ionic nature of CH3COOH by writing it as CH3COO- and H+.

 

[marsenal]

Fair enough. That's preety stupid of me to not have realised that. Oh well. Thanks abdooo. What is with that name btw?

 

[abdooooo!!!]

why? don't you like the name abdoooooooo...? its such cool name. i reckon it sounds way better than the name marsenal...

... just joking; but arsenal sucks anyway, leeds rule!!!

 

[marsenal]

Maybe it does, but there is no way that you can say that Arsenal suck. You just gotta love watching them play. They play like football is meant to played, very free flowing and they share the ball around. And Henry is an absolute champ. But I don't mind Leeds. They've had a bit of a shocker this season though. Btw Arsenal v Leeds 4th May at Highbury.
Geez I hope we take the double again this season. Go you good thing

 

[Twintip]

Remeber to include state symbols in case they dedicate a mark towards them.

 

[abdooooo!!!]

Originally posted by marsenal
Maybe it does, but there is no way that you can say that Arsenal suck. You just gotta love watching them play. They play like football is meant to played, very free flowing and they share the ball around. And Henry is an absolute champ. But I don't mind Leeds. They've had a bit of a shocker this season though. Btw Arsenal v Leeds 4th May at Highbury.
Geez I hope we take the double again this season. Go you good thing

i see you are a very big fan of football (or soccer, i never understood why they called rugby 'foot' ball). i follow football too, i know nearly every player in the premier league, i've being following leeds for 6 years now. how long have you been a fan of arsenal?

 

[marsenal]

Originally posted by abdooooo!!!
how long have you been a fan of arsenal?

I've been following the premier league since year 7 (1998) and preety much from the word go I went for the Gunners.