Chemistry 100 level

Question

What is the oxidation number of S in NH₄H₂SO₄?

My professor says the right answer is +5, but Chat GPT says the right answer is +6, and she doesn't include +6 as one of the multiple choice options. Thoughts?

Answer 1

I'm guessing you mean to say (NH₄)₂SO₄ (ammonium sulfate) or NH₄HSO₄ (ammonium bisulfate) as NH₄H₂SO₄ is not a meaningful compound. I would agree with Chat GPT. I would be able to offer a detailed explanation if you schedule time with me.

Answer 2

I have to agree with @Michael X that NH₄H₂SO₄ does not exist. So looking at the other 2 likely possibilities, we have...

NH₄HSO₄ and (NH₄)₂SO₄

To find the oxidation number of S, we look at the oxidation numbers of the other elements and from that, we deduce the number for S.

Both NH₄HSO₄ and (NH₄)₂SO₄ are neutral compounds (they have no net charge). NH₄ has a charge of +1.

For NH₄HSO₄, HSO₄ therefore is -1. Since H is +1 and each O is -2, that totals -7. By simply subtraction, that means that S must be +6 in order for the HSO₄ to total -1. So, oxidation number of S is +6

For (NH₄)₂SO_4, again, NH₄ is +1, leaving SO₄ to be -2 since there are 2 NH₄ moieties. The 4 oxygens total -8 so for the SO₄ to be -2, the S must be + 6. Again, oxidation number of S is +6.

Now, IF the original structure NH₄H₂SO₄ were to exist, and applying the same rationale as above, we would calculate the oxidation number of S to be +5, as your professor states. So maybe this was a trick question, and a poor one at that. NH₄ = +1; 2H = +2; 2O = -8 so S = +5 (all must add to zero since there is no charge on the molecule).

Answer 3

What is the oxidation number of S in NH₄H₂SO₄?

Yes, agree with the other awesome answers.

This compound should have a negative 1 charge not neutral, because the polyatomic NH₄ has a positive 1 charge, 2 hydrogen have a positive 2 charge, and the SO₄ has a negative 2 charge. This would give the molecule a overall negative 1 charge

Just looking at SO₄

SO₄ is a polyatomic called sulfate , it has a charge of negative 2.

In other words 1 S and 4 oxygen atoms oxidation charges have to add up to negative 2. Oxygen is normally has an oxidation number of negative 2.

Solve for the oxidation charge of S

S + 4(-2) = -2

S=+6