Posted by Cathy on .
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

Chemistry 
DrBob222,
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.