How could you distinguish between the gases h2 and no2?

Explanation:

A molecule is defined as a substance which contains chemically bonded same type of elements.

For example, is a molecule and it exists as a gas which is colorless and odorless.  

Hydrogen gas is represented as .

Whereas a compound is defined as a substance which contains chemically bonded different type of elements in a fixed ratio by mass.

For example, is a compound and has a reddish brown color with toxic odor.

Nitrogen dioxide is represented as .