In the given reaction:
`2NO (g) + O_2 (g) -> 2NO_2 (g)`
nitric oxide reacts with oxygen and forms nitrogen dioxide.
Using stoichiometry, 2 moles of nitric oxide reacts with 1 mole of oxygen and generates 2 moles of nitrogen dioxide.
The rate of nitric oxide reaction (or consumption) at a particular moment is given as 0.044 M/s. Since 2 moles of nitric oxide are forming 2 moles of nitrogen dioxide 0.044 M/s of nitrogen dioxide is being formed.
Since 2 moles of nitric oxide reacts with 1 mole of oxygen, the rate of reaction of oxygen would be half of nitric oxide. In other words, at that particular instant, oxygen would be reacting at 0.022 M/s (= 0.044/2 M/s).
Thus, using stoichiometry and a balanced chemical equation, we can determine the rate of reactions (consumption or formation) for various chemical compounds.
Hope this helps.