Question

1. A scientist studies the reaction 2NO2(g) 2NO(g) + O2(g). She performs three experiments using different concentrations of NO2 and measures the initial reaction rate.
Experiment : [NO2] (mol/L) : Initial Rate ((mol/L)/s)
1 : 0.1 : 0.006
2 : 0.3 : 0.054
3 : 0.5 : 0.150
A. What is the ratio of the concentrations between Trials 1 and 2? (2 points)

B. What is the ratio of the initial reaction rates between Trials 1 and 2? (2 points)

C. What is the exponent for [NO2] in the rate law? (2 points)

D. Write the rate law. (2 points)

E. Solve for the value of k. (2 points)

F. What is the overall reaction order? (2 points)

Answer 1

A. The concentration ratio between trials 2 and 1 is: 0.3 / 0.1 = 3.
B. The ratio between reaction rates is: 0.054 / 0.006 = 9.
C. We solve the equation: (concentration ratio)^x = (reaction rate ratio): $3^x = 9$, which gives x = 2, and the exponent in the rate law is 2.
D. The rate law will have the equation: r = k[NO2]^2
E. To solve for k, we can substitute the values for [NO2] = 0.1, rate = 0.006. This gives: $0.006 = k(0.1)^2$, which yields k = 0.6 L/mol-s.
F. Since the exponent is 2, this is a second-order reaction.