5.
Mandatory Essay –Kinetics---9 points total In an essay of this type, be sure to read the prompt and address whatever is asked. 2 NO2 (g) ÿ2 NO (g)+ O2 (g)(a) Complete the graph. Label the reactant and each product. (3pt)
1point for [NO
2
] decreasing and leveling off
1 point for [NO] and [O
2
] increasing
1 point for [NO] having a steeper curve than [O
2
] since the ratio is 2:1
(b)Answer the questions using data given: (i)Write rate-law and justify. (1pt)
]
(1pt) When experimental data is given with concentration and time, the order is determined from graphical means. A straight line for the following will yield the orders listed:
2
Graph
Order
ln [A] vs time
first
1/[A] vs time
second
[A] vs time
zero
These are listed from most common to least common in frequency.
(1pt)
(ii)
How to find rate constant, k.
The slope of the straight line in the second graph, 1/[NO
2
] vs. time equals
the rate constant and 1/ [NO
2
] is the y-intercept.
[
]
[
]
2
2
o
1
1
= kt +
NO
NO
y
=
mx +
b
(1pt)
(iii)
The units for a second order reaction:
L/mol·s
(or M
-1
s
-1
)
(c)
time (sec)
0
50
100
150
200
250
300
350
400
(1pt) (i) Write a balanced equation from mechanism. Cancel common terms from both sides.
2
2
2
(ii) Which is rate-determining step and why?
