Cliffs AP Chemistry, 3rd Edition

5. The rate-determining step of a several-step reaction mechanism has been determined
   to be

3X(g) + 2Y(g) →4Z(g)

When 3.0 moles of gas X and 2.0 moles of gas Y are placed in a 5.0-liter vessel, the

initial rate of the reaction is found to be 0.45 mole/liter ⋅min. What is the rate constant

for the reaction?

A.

.

.

.

.

.

50

30

50

20

045

32

ccmm

B.

..

.

30 20

045

^^hh

C.

.

.

.

.

.

50

30

50

20

045

23

ccmm

D.

.

.

.

.

.

50

30

50

20

045

ccmm

E..

..

045

^^30 20hh^33

Answer: A

Given a reaction mechanism, the order with respect to each reactant is its coefficient in the
chemical equation for that step. The slowest step is the rate-determining step, so

rate = k[X]^3 [Y]^2

.

.

.

.

k. min

XY

50

30

50

20

rate 045

liters

moles

liters

moles

mole/liter

32 3 2

== :

66 @@ccmm

Kinetics