Considering the rate law for the reaction 2NO + O2 → 2NO2, which of the following could be a possible rate law expression?

• A. rate = k[NO]^2[O2]
• B. rate = k[NO][O2]
• C. rate = k[NO][O2]^2
• D. rate = k[NO2]^2

Answer: (A)

Verified step by step guidance

1. Identify the reaction given: 2NO + O2 → 2NO2. The rate law expresses how the rate depends on the concentration of reactants.
2. Recall that the rate law is generally determined experimentally and is written as rate = k[Reactant1]^m[Reactant2]^n, where m and n are the reaction orders with respect to each reactant.
3. Since the reaction involves NO and O2 as reactants, the rate law will include their concentrations raised to some powers, but it will not include the product NO2 because rate laws depend on reactants, not products.
4. Look at the stoichiometry: 2NO suggests the reaction might be second order in NO, and O2 is likely first order, so a plausible rate law is rate = k[NO]^2[O2].
5. Compare the given options to this reasoning: rate = k[NO]^2[O2] fits the expected form, while the others either have incorrect orders or include the product, which is not typical for a rate law.