Question

Can we use O2 to identify NO and SO2 from each other?
Is it because NO+O2-->NO2; NO2 - brownish gas
and

2SO2+O2--2SO3;SO3-blue in colour?

Or what is the reason?

Answer 1

You are asking, "Can we use O2 to ....". The odor of NO2 (and the brownish color) will identify NO2. Is SO3 bluish colored? I wasn't aware of that but it could be true and it certainly isn't brownish; however, the odor of SO3 is distinctly different than that of NO2. Having said all of this I would look at other methods of distinguishing them. The odor of NO and SO2 is distinctly different. Why go through the oxidation with O2. A quick smell and you will know what is the container.

Answer 2

Actually the question is about identifying each other with O2

Answer 3

Then I think you answer is ok except that I would use odor to identify SO3 as a back up to the color.