Weird oxidation state rule exception for KClO

[DangerRoss]

For potassium hypochlorite (KClO), oxidation state for each atom is

K: +1
Cl: +1
O: -2

O and K both have expected oxidation state, but Cl has the state of +1 instead of -1 that's typically expected.

1) Is there any other exception like this that I should be aware of?
2) Why is that only Cl has the unexpected oxidation state and not other two? How do we figure this out when we see problems like this on the test?

I'd appreciate any input. Thanks!

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[axo86]

The reason why chlorine has the unexpected oxidation state rather than oxygen is because oxygen is more electronegative. You can expect weird halogen oxidation states when bound to oxygen or nitrogen (depending on the halogen), or when the halogen is bound to a more electronegative halogen (for example chlorine monofluoride!) You can always use the method I mentioned in the other post to determine this kind of "exception."

 

[Rabolisk]

This isn't weird nor is it a rule exception. The rule is that the sum of oxidation states of constituent elements add up to the overall charge of the molecule. The rule is that fluorine is always -1, oxygen is almost always -2, alkali metals are +1, and alkaline earth metals are +2.

 

[GyroGyro]

It's not really an exception. In fact, if you look at something like KClO4 you would see Cl has a charge of +7. I believe this was on one of the AMCAS tests.

As others have pointed out, just now the basic rules of group 1, group 2, O (as well as in cases such as H2O2), F.

 

[Temperature101]

For potassium hypochlorite (KClO), oxidation state for each atom is

K: +1
Cl: +1
O: -2

O and K both have expected oxidation state, but Cl has the state of +1 instead of -1 that's typically expected.

1) Is there any other exception like this that I should be aware of?
2) Why is that only Cl has the unexpected oxidation state and not other two? How do we figure this out when we see problems like this on the test?

I'd appreciate any input. Thanks!

The sum of oxidation state of a compound is equal to the charge of the compound. The charge of this compound is zero. Going with your logic, if the oxidation sate of K is +1 and Cl is -1. Do you really think oxygen would be zero? Oxygen is zero when it is in its atomic or molecular forms...Therefore, oxygen cannot be zero in this compound. It has to be -2 and Cl has to be +1. I would be surprised if there is a question like that in the mcat since questions in that test are much more complicated.