Answer

a. The initial concentration of each reactant is equal to the fourth and fifth digits of your Student ID Number divided by 10⁵ M = C_init. (If your ID number is 123456789, then C_init = 45/10⁵ =4.5×10^–4 M.) At some temperature, after 25 s, the concentrations of each reactant are reduced by 15 %.

What is the average rate of reaction for the first 25 s in terms of the loss of [Co(CN)₅]^3–?

Based on the definition of a rate, Rate = [{(100 – 15)/100}×C_init – C_init]/[25 – 0]

b. What is the average rate of reaction for the first 25 s in terms of the gain of NH₃?

The stoichiometric ration between ammonia and the cobalt anion is 5:1, so the rate with respect to ammonia will be 5 times the rate with respect to [Co(CN)₅]^3–

c. The rate law at 25 °C is found to be Rate = k[Co(NH₃)₅Cl²⁺] [Co(CN)₅^3–] with k=5.0×10⁷ M^–1s^–1. What is the initial rate at 25 °C?

[Co(NH₃)₅Cl²⁺] = [Co(CN)₅^3–] = C_init

Rate = (5.0×10⁷)[C_init][C_init]

Specific Answers:

Initial Concentration (M) Final Concentration (M) Rate of Loss (M^–1s^–1) Rate of NH₃ Gain (M^–1s^–1) Initial Rate at 25° (M^–1s^–1)

0.00050 0.00043 -0.0000030 0.000015 -13

0.00052 0.00044 -0.0000031 0.000016 -14

0.00054 0.00046 -0.0000032 0.000016 -15

0.00055 0.00047 -0.0000033 0.000017 -15

0.00056 0.00048 -0.0000034 0.000017 -16

0.00057 0.00048 -0.0000034 0.000017 -16

0.00058 0.00049 -0.0000035 0.000017 -17

0.00059 0.00050 -0.0000035 0.000018 -17

0.00060 0.00051 -0.0000036 0.000018 -18

0.00061 0.00052 -0.0000037 0.000018 -19

0.00062 0.00053 -0.0000037 0.000019 -19

0.00063 0.00054 -0.0000038 0.000019 -20.