For the reaction ,2 O3 —> 3 O2,the reaction rate , delta[O2]/delta t , = 3.0M/min. What is the reaction rate, delta[O3]/delta t, for the same time period?
A) 3.0 M/min B) –3.0M/min C) 2.0 M/min D) –2.0M/min E) .67M/min
2O2 --> 3O2
rate rxn = 1/3(delta O2/delta t)
rate rxn = 1/3(3.0) = 1
rate rxn = -1/2(delta O3/delta t)
(delta O3/delta t) = -rate rxn x 2
-(delta O3/delta t) = -1 x 2 = -2 M/min. Since the O3 is disappearing, that needs to be a -2 M/min.
I think an easier way to do it is the following (just use the coefficients).
(delta O2/delta t) = 3 M/min x (2 moles O3/3 moles O2) = 2.0 M/min and since O3 is disappearing, you must add a negative sign.
To find the reaction rate, delta[O3]/delta t, for the same time period, we can use the stoichiometric coefficients of the reaction.
From the balanced equation, we see that the ratio of the change in moles of O3 to the change in moles of O2 is 2:3.
Given that the reaction rate, delta[O2]/delta t, is 3.0 M/min, it represents the change in concentration of O2 over time.
Since the stoichiometric ratio of O3 to O2 is 2:3, the change in concentration of O3 over time, delta[O3]/delta t, would be (2/3) times the change in concentration of O2 over time.
So, delta[O3]/delta t = (2/3) * 3.0 M/min = 2.0 M/min.
Therefore, the answer is (C) 2.0 M/min.