NAME: 14t(J;.Af{A. ~

PERIOD:

CHAPTER 12

REVIEW PROBLEMS

1. Use the given data for the hypothetical reaction:

2A + B -> products

Reaction # Initial rate (mol/L s)

0.1 0.1 3.0 X 10-2

2 0.1 0.3 3.0 X 10-2

3 0.2 0.3 6.0 X 10-2

(a) Determine the rate law for this reaction.

RATE :: ~< LA]t\ [S]rv1

.03- ::

.03

_ ~ t''l\ - ",-,'

I -v )'1 ( '2',""1-1( (. d , .' J-----')VI( 3)~"1~( (,! I •

::

,0"---,Ob

d-=-JV)

() z: /(b) Calculate the value of the rate constant.

KA~--k .: W-Ol

3.0 y. {O..:..-:----e- I

,--"--'l.1 - I 'I 30 s \\' -1..----

OVER

2. Given the following data for 15.0oC, derive the rate law expression and calculate the rate constant for thereaction:

A + B + 3C --> products

Reaction # IAl lltl [Q Initial rate (rnol/L s)

0.4 0.1 0.1 6.0 x 10-3

2 0.4 0.2 0.1 6.0 x 10-3

3 0.4 0.3 0.2 1.2 x 10-2

4 1.2 0.4 0.2 0.11

(a) Determine the rate law for this reaction.

RAT E z -k lf1J i\ [ gJ "'"[cJ P

• oO~

.00(0=- -

- :;.Ol~

.0010

(b) Calculate the value of the rate constant

o I Iz:

(I. d)J(.J)

:\0.38.).

L01mtA s

It{

- =G. II

.Old

C1 0 I

«ATE ~ J, [AJ [ 13 ] [c J

[RATE ~ ...k [IIt[cJ 1

-- ...-.--~

3. The following data were obtained for the reaction

on (aq) + I- (aq) -+ or- (aq) + CI- (aq)

Reaction # Initial rate (moUL s)

.0015 .0015 1.36 X 10-4

2 .0030 .0015 2.72 X 10-4

3 .0015 .0030 2.72 X 10-4

(a) Determine the rate law for this reaction.

RAI\? :: [0 C..@ -] () l-L -J r¥\

a. 7 J. '" to -1./

-l(i. 3<0 ¥- (0

di')::'d.() z: I

'" )....*(.003) (.OOI~ _~< (. 0 0 IS)"' (. 00 Is) M

- -~d.7d.'j.IO- -'-I1.3~ )(/0

)L(.OO\S)Y) (.0003)""

*- (. OC>\ S)'" C. 00 IS) "'"I,

(b) Calculate the value of the rate constant. W\~

~1lE I. 3~~<.:: -:: L·S

[0(1-) [I-) C. COIS ~s ~ )

z: \100.4 1.s 1(c) Calculate the rate when [OCI"] = 0.0020 mol/L and [1-]= 0.0050 mol/L.

M~:: --k [OCl- J [1."]

~ (1.0. <l ±S) ('00 ;).0'~fh(.OOSO ~ )

=flo.O ~~O -~ E.f IOVER

4. The following data were measured for the reaction

2

[BF31 (mol/L) [NH31 (mol/L) Initial Rate (rnol/L . s)

0.250 0.250 0.2130 'I )"'1r''f ' IIq3 J<(. 3S0) (.100

::=::.0 $q~0.250 0.125 0.1065 r: )< (;I1S)f\ (,100)""S

0.200 0.100 0.0682 d~.;>. z:

0.350 0.100 0.1193f\: I

0.175 0.100 0.0596

3

4

5

a. Determine the rate law for the reaction.

.Olll()

. tOlaS

J;. ('.;l SO) 'I C. cJ.$ 0) ""

..t.(. ~S.O)'" (.laS)"1

b. Determine the overall order of the reaction.

c. Determine the value of the rate constant.

R~TE.= k [eSJ[IJ\-h].0)\30 z: .k (.J.so)(.aso)~---t:

~. <.f I• .:>, ~oC' d. so) 2.

::.

d. Determine the rate when [BF3] = 0.100 molfL and [NH3) = 0.500 mol/L.

M~ z X. [L'>t;J [~nfJJ

( 3 . l( r M~ . S ) (M.~)' ~)

.100 -C (,SOD t:'

O,llO<.{ "'~-- L'S

lno n<\~ 1.: l' S 'j

. _. ._-_ .. __ ..._. - - ._- -----.-- .... -. ---

5. A certain reaction has the following general form:

aA ---> bB

At a particular temperature and [A]o = 2.00 x 10-2 M, concentration vs. time data were collected for this reaction,and a plot ofln[A] versus time resulted in a straight line with a slope value of -2.97 x 10-2 min-I.

a. Determine the rate law, the integrated rate law, and the value of the rate constant for this reaction.

RATE ~ ~ l'-'J= - ~t + & [A J 1)

.: -k

c:: a1Afl ;>

-;Jd. q 7 X 10 J'YIifl-/

b. Determine the half-life for this reaction., (pq 3

n -c;l • -/~. "1 ") 'I. 10 1I((lt=

c. How much time is required for the concentration of A to decrease to 2.50 x 10-3 M?

(d. q1'"(O - iJ, ) +(.0 ()97)1.

OVER

6. The reaction

A--+B+C

is known to be zero order in A and to have a rate constant of 5.0 x 10-2 mol/L s at 25.0aC. An experiment was run at25.0aC where [A], = 1.0 x 10-3 M.

a. Write the integrated rate law for this reaction.

-~ ~(_ S.OO 'j. /0 M) ~L.s T-I (

-3 M.~)/.0 YIO L

b. Calculate the half-life for this reaction.

t.L LA] 02- .: -~.A(

.00/z: ~(do. )C.OS)

\0.01 s)c. Calculate the concentration ofB after 5.0 x 10-3 s has elapsed. Mv-f

- "lA 1 .s: - C.O 5') (.00 S) 4 . (90 1=-7. So 'f.. {O L- I{ ••••v-i "tJ

S -'I ~~ R . '.J- d. -SoY (0 L V"o~tA. 7. So Y. 10 L o/; /l£.N>'\.{X,(;'lW -u ~ '

~' J(J1 ~ I ~ '2 A Ai ~ 1~u-4 (/6rS_1o

l[~J .~J ~"i~"fJ7, The first order rate constant for the radioactive decay of radium-223 is 0,0606 day". What is the half-life ofradium-223?

-[1- .~q3- -d.. - .A<.

= '~C\~. 0(,0 ~

._.__ ._.-.__ ._----_. - ._----_._-------_._._-

8. For the reaction: A -> products successive half-lives are observed to be 10.0,20.0, and 40.0 minutes for anexperiment in which [A]o = 0.10 M. Assuming the reaction is second order, calculate the concentration of A at thefollowing times: I

a. 80.0 mint-.L -z.. -

= J:.t +

-'-[~1 ::(I.0)( 80.0 ) .,. • I

I .

~] = 90

~b. 3~umm

r.cM~' M.lt'\

I .-!--- Jd~ [t\] 0[t:>.J

z: +

.r, ~

[AJ = (I. b ) (30.0) of- . I1 VY\~.i..

~O \ [AJ z: CJ.O';}S L-

[~] ~

9. For the reaction

2 N02 (g) -> 2 NO (g) + 02 (g)

The rate law is

Rate = (1.4 x 10-10 Llmol . s) [N02]2

(a) 1f3.00 mol ofN02 is initially present in a sealed 2.00 L container at 25.00C, what is the half-life of the reaction?J-At. [AJot.L- •••

2... -

: (I. l( ...,.10- 10) ( /. SO)

9'-/. 7 fo X ID .3 IS 18's:

(b) What concentration ofN02 remains after 115 years?I --L-

[A) =- j(.t -t (AJo

t. 17 <f 3lf~ J& 7CEE:-[~r-)J-:::-{)-,-~-S.)-~-~-;-.'

OVER

10. For the reaction

the proposed mechanism is'

(i) MO(CO)6 ~ Mo(CO)s + CO

a. Disregarding the absence of information regarding the rate law, is the proposed mechanism consistent withthe equation for the overall reaction?

'If.5

b. What is the molecularity of each step of the mechanism?I: UtJl (Y\OLECUL41(

s : to\MOl~eVLAt<.c. Identify the intermediate(s).

11. The decomposition of nitrous oxide, N20, is believed to occur by a two-step mechanism:

N20 (g) ~ N2(g) + 0 (g) (slow)

N20 (g) + 0 (g) ~ N2 (g) + 02 (g) (fast)

a. Write the equation for the overall reaction.

b. Write the rate law for the overall reaction.

12. Ozone reacts with nitrogen dioxide to produce Dinitrogen pentoxide and oxygen:

The reaction is believed to occur in two steps:

The experimental rate law is:

What can you say about the relative rates of the two steps of the proposed mechanism?

S~ Ju ~ i: ~(J{A¥V' .i: Jh hn~~ ~ ~+' ~)1): ffluuJ k ;tk ~ ~(lm-'rJ .o1if #

13. The gas phase reaction between methane and diatomic sulfur is given by the equation:

At 550°C the rate constant for this reaction is 1.1 Llmol s and at 625°C the rate constant is 6.4 Llmol s. Using thesevalues, calculate E. for this reaction.

~ (~) = 5;-( I

T,

~(~)I. I:;

OVER

14. The activation energy for the reaction

H2 (g) + h (g) --> 2 HI (g)

is 167 kJ/mo!. The rate constant at 302°C is 2.45 x 10-4 Limo!. What is the rate constant for this reaction at 205°C?

~(~I): ~~(~I

t; (:~:~1O-4) = (.i:S1.5.

(.A'- ~ )

~ .;1., l( S'IIO-q

.J( ),

::

_'7.0~&S3J.3(,

e ------r -7d.O</XIO

=L.

IS. The rate constants for the decomposition of acetaldehyde

CH3CHO (g) --> C~ (g) + CO (g)

were measured at five different temperatures. A plot of In(k) versus IIT produced a straight line with a slope of -2.09 x 104 K. and a y-intercept of -0.45.

(a) Determine the activation energy for this reaction.

E~ ~ K~ z: - d ,00, '" 10

Eo.. z , g-. '0' 4 ~) (». 0 tt Y (0,..::..",_1<_) ---,

I ~.~j-I. 7 l{ Y. fO.s Zvl = 1 7 L{ '''t'-i'-- ---.J

(b) Determine the value of the frequency factor for this reaction.

~ A.:- - 0.4.5-0.4.5

ft.:- e(c) Calculate the value of the rate constant at 537°C.

~ k ::(-~~)( ;:) + ~ AI

(~.oq ~t()'1 1<-) ( 810iL)

A c£kt~to

)tv. Cld~vrJ;.;',\.

16. What part of the energy profile of a reaction is affected by a catalyst?

I~ L J, I I ~ .11 I •~ .:AJ7lL Aafi.[ ~-D /JL().cX~«rtV -'0 LvU\QN au,;t.£I!lv.v(J

~ '" Jcj~"';'(J e. t-r-s ~.17. What is the difference between a homogeneous and a heterogeneous catalyst?

4 hv"»ta-r't~/tJ~vt A.J-IJA

OVER