Cliffs AP Chemistry, 3rd Edition

./

./

2

3

270 10

540 10

rate

rate

mole liter sec

mole liter sec

7

7

#:

= #:

..

..

k

k

0 100 0 010

0 200 0 010

MM

MM

nm

nm

=

^^

^^

hh

hh

= 2.00 = (2.00)nn= 1

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

(b) Restatement: Overall order. Explain.

overall order = m + n = 1 + 1 = 2

The rate is proportional to the product of the concentrations of the two reactants:

2 NO 2 (g) + Cl 2 (g) →2 NO 2 Cl(g)

rate t k

NO

∆ NO Cl

∆ 2

= 22

• =

6

66

@

@@

or

rate t k

Cl

∆ NO Cl

2 ∆ 2

= = 22

• 6
  66

@

@@

(c) Restatement: Rate-specific constant k.

rate = k[NO 2 ][Cl 2 ]

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

..

.

0 100 0 005

135 10

mole liter mole liter

mole liter sec

11

711

::

= #::

--

---

__ii

= 2.7 × 10 –4liter/mole ⋅sec

(d) Restatement: In experiment 3, initial rate of decrease of [Cl 2 ].

2 NO 2 (g) + Cl 2 (g) →2 NO 2 Cl(g)

d

dt

d

dt

Cl NO Cl

2

• 6622 @@= (^1) dn
  = –(5.40 × 10 –7) / 2

= –2.7 × 10 –7mole ⋅liter–1⋅sec–1

(e) Restatement: Possible mechanism.

The proposed mechanism must satisfy two requirements:

(1) The sum of the steps must give a balanced equation.

(2) The mechanism must agree with the experimentally determined rate law.

NO 22 ____ggiiii++Cl k^1 NO Cl 2 ggCl slow

Cl___ggiii+NO 22 k^2 NO Cl gfast

Part II: Specific Topics