Elementary reaction rate

[Cristian Carrasco 1F]

When finding the elementary reaction rate, do we use the coefficients of the reactants?

[Isabella Sanzi 2E]

Because it's an elementary reaction (so basically a step of a reaction), we use the coefficients to determine the order of the specific reactant for the rate law. To illustrate, question 49 lists two different elementary reactions. Step one is HBr + NO2 --> HOBr + NO. The rate law for this elementary reaction is: rate = k[HBr][NO2] (since the coefficients of both of these reactants is 1, they are both first order in the rate law).