Question

Initial Concentration mol/L[A] Initial Concentration mol/L[B] Initial Rate mol/Ls 0.20 0.10 20 0.20 0.20 40 0.40 0.20 160 Given the data in the accompanying table, what is the reaction order for A when comparing the second and third rows?

Answer 1

Answer: 2

Explanation:

1) Table (given):

Initial Concentration mol/L   Initial Concentration mol/     Initial Rate mol/Ls
              [A]                                      [B]                                  

0.20                                               0.10                                     20
0.20                                               0.20                                     40
0.40                                               0.20                                   160

2) Procedure

i) Start assuming the form of the law: r = k [A]ᵃ [B]ᵇ

ii) Comparing row 2 with row 3, you infere that doubling the initial concentration of A and keeping the concentration of B constant, the speed of the reaction quadruples.

That means that the exponent a, or the order of reaction for the reactant A is 2.