[Frith 08]

How do write an ionic equation for the following by elliminating the spectator ions:

2Nacl + Pb(NO₃)₂  2NaNo₃ + PbCl₂

I'm not sure but is this how it should go:
2Nacl (aq) + Pb(NO₃)₂ (aq)   PbCl₂(s)

or Pb (aq) + 2Cl (aq)  PbCl₂ (s)

The next one I'm confused because I think all of subtances are soluable

2 KCL + Zn (NO3)2 ZnCl2 + 2KNO3

[Arkcon]

Well, for starters, you want to write ionic equations, without spectator ions.  So the ionic, dissolved elements should be written as ions -- with their charges, like ⁺, or ^-2, attached to the chemical symbol.  Start with that and see if anything else jumps out at you.

[cliverlong]

I had never come across the term "spectator ion" until I read this forum.

It is a grand term for a rather trivial idea.

Basically (in all the examples I have seen) you take two ionic compounds (salts) that are both soluble in water. In water all the ions are "free" so it makes little sense to write or talk about dissolved NaCl or dissolved PbNO₃ as actual "compounds". However, we write NaCl(aq) and PbNO₃(aq) to indicate that when dissolved in water the ions are liberated from tjhese salts.

Now what happens when we mix these solutions? One of the possible combinations forms an insoluble precipitate that drops out of solution as a solid. All the other ions from the reactants remain in solution. These "unreacted" ions are in the same state before mixing as after mixing i.e. floating around in solution - they are said to "spectate" because they do not participate in chemical reactions (we don't consider dissolving in water a chemical reaction - it is more a physical process).

Now, go back to the original balanced equation. Work out what ions exist when the reacts are in aqueous solution. Delete any non-reacting or spectating ions from the equation. You are left with the reacting ions. You may need to add electron gain or removal to balance the equation.


Clive

[Borek]

I had never come across the term "spectator ion" until I read this forum.

http://www.google.com/search?hl=en&rls=en&q=spectator+ion&btnG=Search

400k hits. Not bad

[cliverlong]

I had never come across the term "spectator ion" until I read this forum.

http://www.google.com/search?hl=en&rls=en&q=spectator+ion&btnG=Search

400k hits. Not bad

I have led a sheltered life.

[macman104]

I'm surprised too that you've never heard the term spectator ion?  Did you ever write net ionic equations?  If you did, did you give a name to the "spectator ion" type umm..thingy?