Why Are Net Ionic Equations Important?

[gsingh2011]

Is the only purpose of net ionic equations to see which elements were oxidized or reduced? Or is there another reason why it is useful?

 

[SlidemanD]

Personally, I don't want to write down all the spectator ions all the time. It just saves time and effort not to write down things that don't react at all.

 

[Borek]

They helps concentrate on what is really happening.

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methods

 

[gsingh2011]

But in neutralization reactions for example, a lot of the time you're just going to get H2O->(H+)+(OH-). The ions that make up the salt cancel out and now you're left with only the dissociation of water. I still consider what happens to those ions important... I don't see any benefit in just seeing water in the equation. So when would a net ionic equation help? You can't say that you see what's really happening, because a salt is being made in this reaction and you wouldn't know by the given equation.

 

[Borek]

I still consider what happens to those ions important...

And what have happened to them? Nothing. They were freely flowing in the solution and they are freely flowing in the solution. Changes to the solution properties have their source in neutralization reaction.

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[somasimple]

Borek,

You're saying that ions are "free" but many books say they are hydrated. They are quite neutralized.

 

[Borek]

Yes, they are hydrated - but as hydrated they are freely moving in the solution. That is not changing regardless of what have happened to OH^- and H⁺.

If we want to get deeper into details we can also differentiate between ions that get hydrated just because they are charged and water molecules are diploes, and those that are complexed by water molecules and surrounded by more or less ordered water dipoles later. Regardless of which model applies, I treat such an ion as a free one, even if technically its description can be quite complicated.

No iodea what you mean by "they are neutralized".

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[somasimple]

An hydrated ion (charged) has a water armor around it.
Thus the charge is made farer from any other ion. Its charge is lowered by this distance and electrostatic bond.
Its motion may be slowed (Na⁺, Ca⁺⁺) or quite favored (K⁺).
It is the famous Hoffmeister series.

 

[Borek]

Charge is not lowered, if anything, it is screened. And yes, water presence has many effects on what is happening in the solution. Is it in any way related to the original question about net ionic equations?

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[somasimple]

Borek,
An elestrostatic bond of any kind is a charge sharing. A share is a share. Then this shared part becomes unavailable for other ions. That is the lowering I'm talking.

 

[Borek]

How is it realated to the original question? If your plan was to confuse OP you already succeded. EOT.

 

[somasimple]

They helps concentrate on what is really happening.

Sorry for the confusion. You were talking about another kind of reality?

 

[PhaseShifter]

Is the only purpose of net ionic equations to see which elements were oxidized or reduced? Or is there another reason why it is useful?

A net ionic reaction will also show you when ions form a crystal lattice and precipitate out of solution.

It also shows when a covalent molecule dissociates into ions. $$NH_{3}+H_{2}O \rightleftharpoons NH_{4}^{+}+OH^{-}$$

(or better) $$NH_{3}+H_{2}O +CO_{2} \rightleftharpoons NH_{4}^{+}+HCO_{3}^{-}$$