Consider the following redox reaction: 2HNO3+ 3H2S –––> 2NO + 3S + 4H2O The nitrogen in HNO3, undergoes: a. reduction b. oxidation c. electrolysis d. neutralization e. decomposition

Question

I have been stuck on this for a bit. Help would be great!

Answer 1

Hey Kai! I'd be more than happy to help you with this!

So, before we start, we can already throw out answer choices c and d because we know this is a redox (reduction and oxidation) problem, meaning the elements either go through reduction or oxidation. That leaves us with a and b.

Using our rules for oxidation numbers in redox reactions, we know that H is usually +1 and O is usually +2. Knowing this information, we can find the oxidation number of N in HNO₃ and NO. Once we find them, we will compare the two to determine whether N underwent oxidation or reduction.

HNO₃ is a neutral compound meaning the overall oxidation number for HNO₃ is zero. This means the oxidation numbers of H, N, and O have to combine to equal zero. We know that H is +1 and O is -2, but there are three of them so it's -6 total, which together is 1-6= -5. This means that N's oxidation number has to be +5 for the total charge to equal zero. Now let's find the oxidation number of N in NO.

NO is also a neutral compound so the overall oxidation number will also be zero. We know that O is -2 so N has to be +2 for the compound to be neutral.

So now we know N has an oxidation number of +5 in HNO₃ but an oxidation number of +2 in NO. The decrease in oxidation number means N gained electrons (number became less positive). The gaining of electrons is called reduction. The answer is a.

Hope this helped! Let me know if you have any additional questions!

Answer 2

First, looking at the oxidation numbers of HNO3, you would find O (-2), N (+5), and H (+1), so (-2*3)+5+1=0. Now, moving onto the product of NO, the oxidation number of oxygen remains unchanged (-2) but nitrogen changes to (+2), so -2+2=0. Therefore, taking a look at the change of nitrogen from +5 to +2, the positive decreases so the negative must increase such that nitrogen gained electrons (negative charge). With this, I believe the answer would be a reduction (recall losing electrons= oxidation and gaining electrons=reduction).