Cliffs AP Chemistry, 3rd Edition

Requirement 1:

22

NO Cl NO Cl Cl

Cl NO NO Cl

NO Cl NO Cl

22 2

22

22 2

"

"

"

++

+

+

Requirement 2:

NO 2 (g) + Cl 2 (g) →NO 2 C1 + Cl

is the rate-determining step. This step is bimolecular.

rate = k 1 [NO 2 ][Cl 2 ]

as found in part (a).

Meeting these two requirements does not prove that this isthe mechanism for the

reaction — only that it could be.

2. Hydrogen peroxide, H 2 O 2 , decomposes by first-order decomposition and has a rate
   constant of 0.015/min at 200°C. Starting with a 0.500 M solution of H 2 O 2 , calculate:

(a) The molarity of H 2 O 2 after 10.00 min

(b) The time it will take for the concentration of H 2 O 2 to go from 0.500 M to

0.150 M

(c) The half-life

Answer

2. Given: H 2 O 2 , first-order decomposition
   k= 0.015/min at 200°C
   [H 2 O 2 ] 0 = 0.500 M

(a) Restatement: Calculate [H 2 O 2 ] after 10.00 min.

For first-order reactions: rate = kX →−dX/dt= kX

Integrating from X 0 to Xgives

ln XX kt

0

-=cm

log X.

Xkt

230

cm^0 =

log..

X

cm0 500M =0 065

.

X

0 500= 10 0 065.

..
X

0 500= 12

.

X.. M

12

==0 500 042

Kinetics