Please help me verify:

Question

The following reactions are involved in the formation of acid rain. Use oxidation numbers to identify which of these reactions are REDOX reactions.

a. 2SO2(g) + O2(g) �� 2SO2(g)
-2 -2 0 -2 -2
No change - not REDOX reacton

b. 3NO2(g) + H2O(l) �� 2HNO3(aq) + NO(g)
-3 -2 +1 -2 +1-3-2 -3-2
Nitrogen and Oxygen are reduced
REDOX reaction has occured

c. SO2(g) + H2O(l) �� H2SO3(aq)
-2-2 +1-2 +1-2-2
Oxygen is reduced
REDOX reaction has occured

Please check...

ps. why would they make a rule for hydrogen in most compounds being +1 when is it not? Same with oxygen being -2.

Answer 1

You still are having trouble with oxidation numbers.
a is not balanced. I think you meant to write
2SO2 + O2 ==> 2SO3
And that is a REDOX equation. S changes from +4 to +6; oxygen changes from zero (the O2 is zero while the O in SO2 is unchanged) to -2 in SO3.

b. You are correct that this is a redox equation but not for the right reasons. N changes from +4 in NO2 on the left to +5 in HNO3 on the right and +2 in NO on the right. Therefore, N in NO2 on the left undergoes both oxidation and reduction. You note that oxygen changes but it doesn't. The oxidation number on the left (in H2O) is -2 and on the right it is -2 in HNO3 and -2 in NO.
c. SO2(g) + H2O(l) �� H2SO3(aq)
S in SO2 is +4 and in H2SO3 is 4. No change. O in SO2 is -2 and O in H2O is -2. ON the right, O in H2SO3 is -2. No change so this is not a redox equation.
Re: your P.S. Because in MOST compounds, H is +1 and in MOST compounds O is -2. H is something other than +1 ONLY in the hydrides (LiH, NaH, KH, CaH2, etc where it is -1). O is other than -2 only in the peroxides (Na2O2, H2O2, K2O2, BaO2, etc where it is -1) AND in the superoxides (KO2, etc where it is -1/2).

Answer 2

Hi yes sorry the arrows didn't work out when I copied the question.

For the following in your answer

2SO2 + O2 ==> 2SO3
And that is a REDOX equation. S changes from +4 to +6; oxygen changes from zero (the O2 is zero while the O in SO2 is unchanged) to -2 in SO3.

Why is S +4? Doesn't S gain 2 electrons hence -2?

I'm using periodic table and S is in group 6A/16 . I thought 6A = 6

This is corrispondence course so all I have done is based on book explanation and my research so I'm not entirely confident on my periodic table use, maybe that is why I'm getting this wrong.

Answer 3

Hi again - was just comparing part c with your notes and I have an extra Oxygen on left side that right side doesn't have?? Perhaps your mistaken and oxygen is reduced?

Answer 4

Please disregard my 2 comments after. I finally had my Eureka moment and figured this all out. Thanks to your help and researching a bit more I feel I understand this now. Your efforts in helping me were not wasted lol. Thanks again!