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CHM 230 CHEMISTRY TWO Fall 2011
EXAM 1
Time: 7:30 p.m. - 8:45 p.m.
I VERSION 1 I
1. Print your name and student 10 number on your scantron' card and fill in the
appropriate circles for your 10 number.
2. Mark your test version number (1 or 2).
3. Use a soft #2 pencil only, and blacken circles completely.
4. If you decide to change an answer, erase the unwanted mark very carefully.
5. If you do not comply with the above requests or if your card is filled out incorrectly,
4 points will be deducted from your exam score.
6. Mark the one best answer to each question. Any question for which more than one
response has been blackened will not be counted.
7. There are 25 questions in this exam and your score is based solely on the number
of questions you answer correctly.
In [A]t =-kt 0.693^1 1 1 k = Ae-Ea/RT
11 =-- -==kt+- 11 =-
[A] 0 ' - 2 k^ [A]t [A]o ' 2 k[A]o
In~= Ea[_1 _~] (^) R =8.314 J mor^1 K-^1 =0.0821 L-atm K-^1 mor^1
k2 R T2 T
PERIODIC TABLE OF TI-IE ELEMENTS
lA (^) 8A roo- 1 ~ H 2A 3A 4A 5A 6A 7A He 1.008 (^) 4. 3 4 5 6 7 8 9 10 Li Be (^) B C N 0 F Ne 6.942 9.012 10.81 12.01 14.01 16.00 (^) 19.00 20. (^11 12 13 14 15 16 17 ) Na Mg 3B 4B 5B 6B 7B 8B 8B 8B IB 2B Al (^) Si P S CI Ar 22.99 24.30 26.98 28.09 30.97 32.06 35.45 (^) 39. (^19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 ) K Ca Sc Ti (^) V Cr Mn Fe Co Ni Cu (^) Zn Ga Ge As Se Br Kr 39.10 40.08 44.96 47.90 50.94 52.00 54.38 55.85 58.93 58.70 63.55 65.39 69.72 (^) 72.59 74.92 78.96 79.90 83. 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr y^ Zr Nb^ Mo^ Tc^ Ru^ Rh^ Pd^ Ag^ Cd^ In Sn^ Sb^ Te I Xe 85.47 87.62 88.91 91.22 92.91 95.94 98 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 127.9 131. 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg TI (^) Pb Bi Po (^) At Rn 132.9 137.3 138.9 178.5 181.0 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 (^) 209.0 209 210 222 87 88 89 104 105 106 107 108 109 110 111 112 114 116 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Duu^ Dub^ Uuq^ Duh (223) (226) (227) (261) (262)^ (266)^ (264)^ (277)^ (268)^ (281)^ (272)^ (285)^ ~ ~ 58 59 60 61 62 63 64 65 66 67 68 69 70 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 140.1 140.9 144.2 145 150.4 152.0 157.3^ 158.9 162.5 164.9 167.3 168.9 173.0 175. 90 91 92 93 94 95 96 97 98 99 100 101 102 103 Th Pa U Np Pu Am em Bk Cf Es Fm Md No Lr 232.0 231.0 238.0 237.0 244 243 247 247 251 252 257 258 259 260
1. Which relationship correctly compares the rates of the following reactants and
products?
C 3 Hs(g) + 5 02(g) ~ 3 CO2(g) + 4 H 2 0(I)
a. rate = ~[C3H8] = ~[02] = ~[C02] = ~[H20]
f1t f1t f1t f1t
b. rate = ~[C3H8] = ~[02] = _~[C02] = _~[H20] f1t f1t f1t f1t
~rate =_~[C3H8] = _1- ~[02] = 1 ~[C02] = 1 ~[H20] ~ f1t 5 f1t 3 f1t 4 f1t
d. rate = ~[C3H8] = 5 ~[02] = _ 3 ~[C02] = _ 4 ~[H20] f1t f1t f1t f1t
e. rate =~[C3H8] = 5 ~[02] = 3 ~[C02] = 4 ~[H20] f1t f1t f1t f1t
~ 2. For the reaction below the rate of disappearance of I-(aq) at a particular time and
concentration is -2.7 x 10-^3 MIs. What is the rate of appearance of 12 ( aq)?
I03-(aq) + 5 I-(aq) + 6 H+(aq) ~ 3 12 (aq) + 3 H 2 0(1)
a. (^) 5.~x 10-^3 MIs ~ =- - ~ ~L:r:-~ ="~ ~-::t:: 2.J
b. 8.1 x 10-^3 MIs G 6t 6t ~ 1.6 x 10-^3 MIs 6 -:J:::-z.--:J. = - ~ ~-=.J
~ L::::.. t s- ,,---
d. 4.5 x 10-^3 MIs r ~t e. 6.2 x 10-^3 MIs ~. - ~ C"2.>1->£ lO~ t--/S) -:::... t'· b x,D'!> -@
3. Nitric oxide gas (NO) reacts with chlorine gas according to the equation:
NO(g) + % CI 2 (g) ~ NOCI(g)
Use the following data to determine the experimental rate law for this reaction.
I Ex^ eriment^ [CI2]^ Initial^ Rate M^ h-
~
a. rate =k[NOl ~ =- 'l:-~oJLC.\7-Jn
b. rate =k[NO][CI2l 1/2 T o^ -Rrd. ~ ~ l.'5e:- ~f> . + 2.
c. rate^ =k[NO][CI2l^ ?-~^ '=^ It^ 'f'<..^ ::::-^ 2..^ J
® rate =k[NO]2[CI2] To ~~ ~ '. ~s.e ~=> '2--+ S
e. rate =k[NO]2[CI2]2 '2 '"' = '2-. ~ f"' ~ \ \
- (^) It takes 42 min for'the concentration of a reactant in a first-order reaction to drop
from O.45M to 0.32M at 25°C. How long will it take for the reaction to be 90% complete? '. U ']
a. 13 min \ ('\ f1 t- - - l,C ::::- t r'. ~o~o -=-,c 'is" I l ~ l 0 ~lh-0 t
r!T]o (000)0 l "') b. 86 min
c. 137 min^ \0.^ (^ 0·""3:-^ .^ -=-^ -^ ~q--z.^ M~f)^ ')^ -^ 2 ·~o^ :=t^ "6^ ·^ x^10 ~Miirl-)^ t l O-UcS )
ev
d. 222 min ~o.~Lt =- _ \C...C~2M~{') t = '2..'3,0 3 <tS ~ \ X\O MlA-' e. 284 min -~ '- -\ [ hi K =- '15. \ x. \0 fV\ \f) _ t.::: 2.~ It- M~~
- A chemical reaction that is first-order in X is observed to have a rate constant of
1.9 x 10-^2 S-1. If the initial concentration of X is 1.0 M, what is the concentration of
X after 205 s? .. (~ ,- \ ~ ~ =- . q x \ D -:;-\ X2-^0 S s ) a. 49 M '.OM' b. 0.61 M
c. 0.20 M
d. 0.98 M
<9 O.020M
\ X=-o ,0"2.0 8
8. The reaction A + 2B -7' products has the rate law, rate = k[A]2[B]2. If the
concentration of A is tripled and the concentration of B is halved, by what factor will the rate of reaction change?
a. 9.
b. 4.
c. 3.50 ~^ =0..^ ~^ LJ-O.:J.2-IT-OJL^ =-^ ~
Rd!e.::: K-. @~o-:J-z.l9~sJ2. :=t2-2~ e. 1. A- (-5 tr.~-ed 13 lS t'c:U.~
- For^ a chemical reaction, the activation energy^ for^ the forward reaction is +155 kJ and the activation energy for the reverse reaction is +117 kJ. What is the enthalpy change, ~H, for the forward reaction?
+38 kJ
+155 kJ +272 kJ
a. -272 kJ
b. -38 kJ
e.
@ d.
10. The rate constant for a first-order reaction is 1.8 x 10.^2 S·1 at 690 K and 3.6 x 10.^2
S·1 at 876 K. What is the activation energy?
a. 8.1 kJ/mol \f".{£' ) ~E~ ~~ - ~:J ® 19 kJ/mol \¥-"2- \C... [ -J
:~ ::Ok~/~:~OI \l~'~~~;~:~) ~ E~ ~~b~- 6~DJ
e. 80 kJ/mol .... 0. bet s t:~ ~------
(~~ - b~CK)
Ed,.
- The rate constant for a first-order reaction at 25°C is 3.32 x 10.^10 S·1. (^) Calculate
the rate constant at 40°C if the activation energy is 116 kJ/mol.
a. 8.71 x 10-^5 S-1 e'"' \C.- \ .:::.t:.o-....\ ~ lJ-'. ® 3.12x10-^9 S-^1 --y:; \2.- L"2- T\
c 4.64 x 105 S·1 -\
. " 'S4SLX \tJ 5-\
d. 5.05 x 10.^8 S·
e. 3.96 x 104 S·
K-z
--\0 ,
S "s?-X\O .~-
'v:-.. -z.
12. Which of the following statements is incorrect concerning a catalyst?
a. A catalyst decreases the activation energy of a reaction. T nA.SL
b. A catalyst provides an alternative reaction mechanism. True..
cD A catalyst alters the equilibrium concentration of reactants and products.
d. A catalyst does not change the enthalpy of the reaction. ~
e. There is no net consumption of a catalyst in a reaction. 1f'1A.<
c.
d. 1.5 x 10^9
e. 3.0x10^9
\
- At 35°C, the equilibrium constant for the reaction:
2 NOCI(g) -~ 2 NO(g) + CI2(g)
is Kc =1.6 x 10-^5. An equilibrium mixture was found to have the following
concentrations of CI2 and NOCI: [CI2] =1.2 x 10-^2 M; [NOCI] =2.8 x 10- 1 M.
Calculate the concentration of NO(g) at equilibrium.
a. 1.0 x 10-^4 M ~^ =^ EJ^0 ~J~-^ @.-^ -z.-)
1.0 x 10-^2 M ~ocDtt..
c. 2.8^ x^ 10-^1 M^ /}JO:J'2.. =. K ft.l0Q.J 7... ":::: Q, 6:X.O-S-)C?-.%,x,o-~) '
d. 2.4^ x^ 10-^2 M^ ts-'l.-3 .. l' r '2-x.lO '2.)
e. 1.6^ x^ 10-^3 M^ l}JoJl...=-. . OL.tS x.O"" {}-jO) =: . 0 x. '-0-2. t-\
17. The^ equilibrium constant^ (Kc)^ for^ the following reaction is^ 6.7^ x 10-^10 at^630 cC.
.N 2(s) + 02(g) -~ 2 NO(g)
What is the equilibrium constant for the reaction below at the same temperature? NO(g) ~- 1/2 N2(g) + 1/2 02(g)
® b.
3.9 X
5.5 X
'"\ha- ~~of'\ ~ ~ ~~ ~
~ ~ c''-I.~ ~ '2.-,
7.5 X 10 8
- Consider the decomposition of dinitrogen tetroxide at 25 ce. N20 4 (g) -~ 2 N0 2 (g) Kp = 0.
What is the partial pressure of N0 2 at equilibrium if the partial pressure of N204 is 0.0549 atm? Kr =
r NC,
a. 0.0158atm
b.
e.
c.
0.0791 atm
0.0209 atm
0.0889 atm
0.0377 atm
D ~
, NO?.
?N~0c.r
K~ ~N1--0tr
Y~
~ ~ • \ 4--'-r )~ ,os-lt-'\ ~
=0. OO~1.
1>NO-z :=: ro ~ CJOT-C' ~
~'f~c~~S
Consider the following reaction at 25°C.
NH 4 H8(s) .~. NH3(g) + H28(g) Kp = 0.
What is Kc for the reaction at 25°C?
a. Kc =9.3 ~ K:? =- Kc:. (\2--,)~f'\
b. Kc =9.3 X 10-^3
<C) K Kc..^ ~^ K-t>
c =1.8^ X^ 10-
4
C¥-)~
d. Kc =1.3^ X^ 10-^4 ~^ ~cJ~^ 2-~q~)J^ Z-
e. Kc =1.2 x 10-^2 =:- \ ~ &' ~ .O-~
The equilibrium constant, Kc, is 6.5 x 10^4 at 35°C for the reaction:
2 NO(g) + CI 2 (g) -<' 2 NOCI(g) "2..., C )(.'-0-' mo \ = .e> x .e:)1- H
2-~C L-
If 2.0 x 10-^2 mol each of NO, CI 2 and NOCI are mixed in a 2.0 L container, ,which
of the following statements is correct about this reaction? a <. K
tf\Q < K, reactants will be converted to products as equilibrium is being Vestablished.
b. Q < K, products will be converted to reactants as equilibrium is being
established.
c. Q > K, reactants will be converted to products as equilibrium is being established.
d. Q > K, products will be converted to reactants as equilibrium is being
established ..
e. the reaction is already at equilibrium, and no further change will take place. Q '=. ~oc-D'2.. ....... l\ ~ 0 X.()-2..) ~ ..' =- \ 00
Consider the following equilibria: ~oJ 'L~~ (\ rO~o-~'"l-C!'O'ILL~~
2 803(g) ~ 2 80 2 (g) + O2 (g) K c = 2.3 x 10-^7
2 N0 3 (g) .~ 2 N0 2 (g) + O 2 (g) K c = 1.4 x 10-^3
Calculate the equilibrium constant for the following reaction:
802(g) + N03(g) ~ 803(g) + N0 2 (g)
@) K^ =78^ ~~~~^ 1- _~. ~^ .~ ~(:)3l"2.~3x.\O\ -:r)~z.
b. K^ =1.3^ x^ 10-^2 C
c. K^ =1.6^ x^ 10-^4 N()^3 *^ N07-^ ..;:-^ ~A^ Q...-)(()-~)?-L
d. K =3.2 x 10-^10 SO-z.. 't l-J03 ~ ~ "3 ~ NO-z..
e. K =6.1 X 103
K =((2-~3X()4-)I" ') ~ 4-XlO~Y2.. .=.ljg J
- Increasing the temperature of the following exothermic reaction will _.
4 N0 2(g) + 02 (g) .~. 2 N 2 0S(g) + heat
a. decrease the amount of O 2 in the system.
b. shift the equilibrium from left to right.
© increase the amount of N02 in the system.
d. increase the amount of N 2 0 Sin the system.
e. none of the above.
