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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: HowDoIScience on October 23, 2018, 11:24:53 AM

Title: Help with Oxidation numbers.
Post by: HowDoIScience on October 23, 2018, 11:24:53 AM
So we had a midterm today and the question was "Which of these compounds has the atom with the highest oxidation number?"

A= CaS
B= Na3N
C= MgSO3
D= Al2O3
E= NH4Cl

I got it wrong in the exam I think so I went and worked it out, I'm pretty sure it was C after I had went back and looked at it.  I got Sulfur with +4 as the reason why it is the atom with the highest oxidation number.

So my friend, bless his patient soul, who is basically a walking encyclopedia, said he worked it out by the transfer of the electrons  (Mg (-2)), (S (+2)), O(+2) in order to gain full shells of electrons. So I'm just wondering is that another way to work out the answer?  I don't want to wreck his head any further. 

So basically I'm asking is there another way to work out oxidation numbers like from the amount of electrons it needs to gain or lose?

And why does Sulfur in MgSO3 have an oxidation number of +4?



Title: Re: Help with Oxidation numbers.
Post by: Borek on October 23, 2018, 12:55:21 PM
First of all - there are simple rules to follow. Do you know them?

http://www.chembuddy.com/?left=balancing-stoichiometry&right=oxidation-numbers-method
Title: Re: Help with Oxidation numbers.
Post by: HowDoIScience on October 23, 2018, 01:10:39 PM
Quote from: Borek on October 23, 2018, 12:55:21 PM
First of all - there are simple rules to follow. Do you know them?

http://www.chembuddy.com/?left=balancing-stoichiometry&right=oxidation-numbers-method

I know most of the rules,  some of them are new in reading that I will admit.

So is that literally the only way to work out the oxidation numbers,  there is no other way? Also is MgSO3 the right answer? 
Title: Re: Help with Oxidation numbers.
Post by: Borek on October 23, 2018, 01:36:28 PM
Quote from: HowDoIScience on October 23, 2018, 01:10:39 PM
So is that literally the only way to work out the oxidation numbers,  there is no other way?

Yes.

Quote
Also is MgSO3 the right answer?

Why don't you try to apply the rules and calculate? That's basically how you do the science.
Title: Re: Help with Oxidation numbers.
Post by: HowDoIScience on October 23, 2018, 02:32:52 PM
Quote from: Borek on October 23, 2018, 01:36:28 PM
Quote from: HowDoIScience on October 23, 2018, 01:10:39 PM
So is that literally the only way to work out the oxidation numbers,  there is no other way?

Yes.

Quote
Also is MgSO3 the right answer?

Why don't you try to apply the rules and calculate? That's basically how you do the science.

I have, but I'm unsure I'm correct,  that is the only reason I'm asking. I've done it for each of the compounds, and I think it's MgSO3 but I'm not one hundred percent positive.
Title: Re: Help with Oxidation numbers.
Post by: chenbeier on October 23, 2018, 03:09:41 PM
Yes you are right Sulphur has the highest oxidation number.
Title: Re: Help with Oxidation numbers.
Post by: Enthalpy on October 29, 2018, 09:39:05 AM
The nearest octet (sulphur gaining 2 electrons) isn't always the sole possibility. Most elements can have many oxidation states. For instance CO and CO2 are both stable.