Question

A chemistry student needs to calculate the rate constant for the following reaction: 2 H2(g) + O2(g) --> 2 H2O(g) The initial concentration of H2 is 0.45 M and the initial concentration of O2 is 0.20 M. The reaction rate is measured to be 0.75 M/s. Calculate the rate constant for the reaction.

Answer 1

To calculate the rate constant for the reaction, we will use the rate law expression. The rate law for a reaction is given by:Rate = k [A]^m [B]^nwhere Rate is the reaction rate, k is the rate constant, [A] and [B] are the concentrations of the reactants, and m and n are the reaction orders with respect to the reactants.For the given reaction:2 H2 g  + O2 g  --> 2 H2O g Let's assume the reaction is first order with respect to both H2 and O2. Then the rate law expression will be:Rate = k [H2]^1 [O2]^1We are given the initial concentrations of H2 and O2, and the reaction rate:[H2] = 0.45 M[O2] = 0.20 MRate = 0.75 M/sNow, we can plug these values into the rate law expression:0.75 M/s = k  0.45 M  0.20 M To solve for k, divide both sides by  0.45 M  0.20 M :k =  0.75 M/s  /   0.45 M  0.20 M  k = 8.33 s^-1The rate constant for the reaction is 8.33 s^-1.