What Are the Spectator Ions in This Chemical Reaction?

[carlodelmundo]

Homework Statement

2KMnO₄ (aq) + 10FeSO₄ + 8H₂SO₄ -->

K₂SO₄ (aq) + 2MnO₄ (aq) + 5Fe₂SO₄ (aq) + 8H₂O (aq)

Homework Equations

Spectator ions don't participate in the reaction.

The Attempt at a Solution

What gives? Is my professor bent on making our lives miserable? The answer for the above is: the spectator ions are K⁺ and SO₄.

I understand spectator ions don't participate in the reaction... but what's so divinely different between K+ and SO4 that isn't happening in the other ions? There are two Sulfate ions in the productsby the way which adds to my confusion...

 

[Borek]

First of all - write everything in dissociated form. It is not called "net ionic" for fun

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[carlodelmundo]

Here are the spectator ions:

2K⁺ + 2MnO₄^- + 10 Fe²⁺ + 10SO₄^2-

yields:

2K⁺ + SO₄^2- + 2MnO₄ + 10Fe¹⁺ + 5SO₄^2- + 8H₂O

Hmm. Interesting that I found the net ionic equation. The only ions I see that are the same are the K⁺ and SO₄^2- ions. The manganate ion, 2MnO₄^- doesn't count because the product MnO₄ is not an ion correct?

And same for the ion right? It's not a spectator ion because one is of +2 charge and the other of +1 charge?

 

[Borek]

Where did you get the original equation from? I must admit I have not taken a closer look before, now that I did rest of the hair on my head rasied up.

But your analysis seems to be OK, only K⁺ and SO₄^2- remain unchanged after the reaction.

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[carlodelmundo]

The original equation was pulled from an old exam of my undergrad chemistry professor. It was a little weird, so it was worth discussing.

Thank you for your analysis and general helpfulness Borek. This question was a bit weird!

 

[Borek]

It was a little weird, so it was worth discussing.

To be honest I hate questions that are based on nonexisting chemistry, they only create confusion.

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Spectator ions, in the context of chemistry and chemical reactions, are ions that do not participate in the chemical reaction. Instead, they remain in solution as either reactants or products, depending on whether they were part of the initial reactants or formed as products during the reaction. Spectator ions are not involved in the actual chemical transformation and do not change their chemical form. Their primary role is to maintain charge neutrality in the solution.

Here's an example to illustrate spectator ions:

Suppose you have a reaction between aqueous solutions of silver nitrate (AgNO3) and sodium chloride (NaCl) to form silver chloride (AgCl) as a precipitate:

Ag⁺(aq) + NO₃⁻(aq) + Na⁺(aq) + Cl⁻(aq) → AgCl(s) + Na⁺(aq) + NO₃⁻(aq)

In this reaction:

• Ag⁺ and NO₃⁻ ions from silver nitrate (AgNO3) are involved in forming AgCl, so they are not spectator ions.
• Na⁺ and Cl⁻ ions from sodium chloride (NaCl) don't change their chemical form during the reaction. They are just "spectators" in the sense that they are present but don't participate in the formation of the AgCl precipitate.

Spectator ions are important to consider in ionic reactions because they help ensure that the overall charge remains balanced in the reaction mixture. While spectator ions don't directly impact the reaction's outcome, they are crucial for maintaining charge neutrality and the ionic balance of the solution.