Chemistry MATH question 3

Question

Determine the rate law and the value of k for the following reaction using the data provided.

 

2 NO(g) + O₂(g) → 2 NO₂(g)     [NO]_i (M)   [O₂]_i (M)   Initial Rate (M^-1s^-1)

                                     0.030       0.0055      8.55 × 10^-3

                                     0.030       0.0110     1.71 × 10^-2

                                     0.060       0.0055     3.42 × 10^-2

Answer 1

Comparing trial 1 and trial 2, [O₂] doubles while [NO] is constant and rate doubles. It is 1st order in O₂

Comparing trial 1 and trial 3, [NO] doubles while [O₂] is constant and rate quadruples. It is 2nd order in NO

Rate = k[NO]²[O₂] ... rate law

Using the rate from any trial above, and solving for k, we have...

8.55x10^-3 = k [0.030]²[0.0055]

8.55x10^-3 = 4.95x10^-6 k

k = 8.55x10^-3 / 4.95x10^-6

k = 1.73x10³ M^-2s^-1