Isn't every reaction REDOX?

[axp107]

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In every reaction, doesn't something gain electrons while something else loses electrons?

C(g) + O2(g) -> CO2

Apparently, this is a combination, combustion, AND a Reduction-Oxidation

Looks like a simple, basic equations .. without even involving ions. How can you tell its a redox equation???

What are distinguishing factors of redox equations when charges aren't given?

Also, this one... is redox

S(s) + O2(g) --> SO2

 

[jochi1543]

Look at the formal charges. In the beginning, we have elementary oxygen and sulphur, with formal charges of zero. As parts of the product, however, they both now have formal charges different from zero. We know it's -2 for oxygen, so in this case, it's +4 for sulphur. So the formal charge on oxygen has gone down (it's been reduced) and the formal charge on sulphur has gone up (it's been oxidized).

 

[axp107]

Can you show me a reaction where formal charges don't change?

 

[jochi1543]

Can you show me a reaction where formal charges don't change?

Hmmm, I'm not a chem major (and only took gen chem I and orgo I ), but I'm thinking an example from the ozone cycle would work:

O3 + O ---> 2O2

Everything is neutral here, if I recall correctly (formal charge of zero).

 

[artaxerxes]

displacement reactions usually,

can't really think of one off the top of my head but you know,

AB+CD-->AD+BC

I'm not sure if this equation is right

C+O2-->CO2, never seen a reaction where carbon on its own combusts

C6O6H14+O2-->H2O+CO2, the O2 is reduced, but nothing is oxidized interms of formal charge, but the I guess you could say that Cis being oxidized by being attached to more Os.

 

[jochi1543]

C+O2-->CO2, never seen a reaction where carbon on its own combusts

Burning coal.👍

EDIT: I actually don't think that reaction qualifies, because both reactant atoms have a zero formal charge, but the product atoms don't.

 

[BerkReviewTeach]

I think you are inadvertently using the term formal charge when you mean oxidation state.

Redox reactions are defined by the change of oxidation state in at least two of the atoms.

In C(gr) + O2(g) <=> CO2(g), the oxidation state of carbon starts at zero (which also happens to be its formal charge, because it is neutral). In the end, it has an oxidation state of +4, because oxygen is more electronegative than carbon, and therefore will pull those electrons from carbon. Having four bonds to oxygen results in the loss of four electrons from carbon to oxygen. Oxidation state is simply book-keeping of what would be expected if the molecules broke apart in a heterolytic fashion.

That said, it is far easier to think of oxidation as a gain of bonds to oxygen (or any more electronegative atom) and/or the loss of bonds to hydrogen (or any less electronegative atom). Reduction is the reverse.

So, in the conversion of C and O2 to CO2, C has gained bonds to oxygen and O2 has lost bonds to oxygen, meaning that C was oxidized and O was reduced.

This can be seen in the conversion of an alcohol into a carbonyl (such as a ketone or aldehyde), where carbon gains a bond to O, meaning it was oxidized.

 

[jochi1543]

I think you are inadvertently using the term formal charge when you mean oxidation state.

You're right...I'm still in the orgo mode.

 

[eggtart]

to add

another reaction that is not a redox reaction is

HCl + NaOH = NaCl + H2O