Rate equation for an elementary reaction Yesterday, I had a debate with a friend of mine over the determination of the rate of elementary reactions. He said:


  Rate equation of elementary reaction can be directly given by just raising the reactants concentration terms to the respective coefficients of the balanced chemical equation whose rate is to be determined. 


and he also gave the example of this reaction

$$\ce{2NO (g) + O2 (g) -&gt; 2NO2 (g)}$$

whose rate is

$$
\ce{[NO]^2[O2]}.
$$

Questions:


Can I write the rate equation of an elementary reaction by just simply looking at the stoichiometric coefficients in the balanced equation and raising them over the concentration of reactants?
Are there any examples of elementary reaction where the exponential powers on the concentration terms in the rate equation comes different than the stoichiometric coefficients of that reaction?
The reaction order with respect to a reactant species cannot be determined from the chemical equation alone. You would have to be given more information. In real life, orders of chemical reactions are found experimentally.