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Unformatted text preview: Chem 202
Fall 2009 SAMPLE EXAM Ell This practice exam is about 2/3 the length of a full exam. Give yourself 35 minutes to work on it.
Formulas and constants, which you may or may not need, are listed below: ﬁonstanta and Conversions
NA = Avogadro's number m 6.022 x 1023 mol‘“1 h m 6.626 x 1034 J a c e 3.00 x108 m e1 charge on one electron : o 21.602 x1049 0 sq m 8.854 x 1012 CZJ”1m“1 me = mass of electron in a vacuum a 9.109 x 10"31 kg .
Space for point totals
1 atomic mass unit 3 1.6605 x 10”27 kg I K==273.15 + “c 1eVa1.602x10“19J 1.1 :1 kg m2 3‘2
HZ a hertz : a“1
k = Boltzmann’s constant x 1.3805 x 1023 J k1 1cm"1:1.987 x1023 J a 2 0.08200 L, atm k“1 moi"1 e 8.314 J k"1 mor‘
760 tort“ : 1 atm 1000 L. = 1 m8
Formulaa hvo e o + (1/2) met/2 % ionic character in bond AeB m (1 , axp[(e1 /4)(XA  XBﬂ) X
100% u r: [r / 0.2082] 8 where u is in Debyes, r is in A E :W nt1,2,3... : e
” 8e0n2h2 r” nZeZme “1’2’3
—h2 d2\y(x h2n2
8mL2 for particle in onewdimeneional box of length L with V(x) w 0 from x e O to Xe L: En ‘5: ne’l 2,3... E} e (hZ/STEZD J (J + 1) where l e [mAmB/(mA += mB]r2 e mreduced r2 for diatomic
molecule AB / k
EV e (ll/271:) W (v + 1/2) where mreduced a: [mAmB/(mA + mg] for diatomic molecule AB PA 3 XAPtolal (1/2>Nam vimsz m (3/2>RT Vrme a V1.3: Vmp *4 V???“ Vav 1““ "87% rm : 47t(m/27ckBT)3/2 v2 exp(~mv2/2kBT) (P + a(n2/V2)) (v m nb) 2 nRT Nile 3 exp HEi ~ Ej)/kBT] (remember that “exp” means “e to the power of”) w m mPextAV w 2: “mm“ ln (vf/vi) w x wnRT In (Pi/Pf) H a: u + ev CV '2“ AU/A‘T Cp 2 All/AT" Cp e CV + F? AS 3 qreV/T AS e (I: In ("Ff/Ti) AS 3 HR In (Vf/Vi) AS e nR ln (Pi/Pf) Asvap e AHvap/Tb
S 2 k an ASeurr e “AHsys/T at constant T, P eod Lucid I. (50 points). Multiple Choice. Circle the letter of the best answer. Five points each. 1. Which one of the following Statements about intermolecular forces is FALSE?
a Hydrogen bonds are generally stronger than London dispersion forces on a per mole
basis. ’t rs ,.
C::} Matter Is fundamentally repulsive, since it Is impossible to solidify helium. i“ » WWMWW c. All intermolecular forces depend on the distance between the two molecules m the closer the molecules are, the stronger the interaction (up to a point). i
d. The strength of interaction between two polar molecules depends on the dipole moments of the two molecules, ”f
e. More than one of the above is false. 2. What kind of intermolecular forces does HF have with itself? a. Induced dipole— induced dipole forces only.
b. Dipole dipole dipole induced dipole, and induced dipole induced dipole forces. ((3 >Dipole dipole dipole induced dipole induced dipole induced dipole forces, and “hydrogen bonding.
d None of the above is correct. 3. Rubidium crystallizes in a bodycentered cubic lattice. The number of Rb atoms in one unit
cell is ﬁprz/Eﬁzm
.  kl
bN—x @0207: 4. if a process can be performed either adiabatically, or not adiabatically, which way produces
the most work? (a) the adiabatic one. be the non adiabatic one. c. the same amount of work is done in both cases. 5. Which one ot the following statements about solids is TRUE?
a. ln crystalline solids, the atoms (or molecules) do not have long”range three, dimensional order.
b. ionic solids are usually easy to melt. . _ My? i c. A metal that crystallizes in a tacemcentered cubic structure is always more
.. 939?? £3 W? dense than one that crystallizes in a primitive cubic unit cell. .Jgatewtw Mesa
(NW 23‘ ‘ {th if you calculate the density of a compound from its unit cell data, you should
(tr/W ‘tgét the same number for density as you would if you measured the density of a bulk sample. stirs” wt tamat;
s. More than one of the above statements is true. 6. it alchemical reaction is endothermic,
tag} the surroundings get colder and colder as the reaction happens.
b. the surroundings get hotter and hotter as the reaction happens.
(3. the surroundings do not change temperature as the reaction happens. “7. If a chemical reaction is spontaneous,
a. it happens quickly.
b. its entropy change has a positive sign.
c. its enthalpy change has a positive sign. f: t T‘} none of the above. W 8. Which of the following is TRUE?
a. The enthalpy of an isolated system tends to increase overtime.
b. The entropy of an isolated system is zero.
{’92: The internal energy of an isolated system is constant.
d. A perfect crystal at absolute zero (temperature) has zero tree energy. 9. Lattice enthalpies...
a. are hundreds of kJ/mol in magnitude.
b. correspond to the enthalpy difference between an ionic solid and its gas phase ions.
0. are hard to measure directly.
d. more than one, but not all, of the above.
(5%; all of the above. 10. Which process produces more work: an ideal gas expanding reversibly and isothermally, or
an ideal gas just expanding?
:3 Neither: the amount of work done is the same if the change in volume is the same.
£15.} Reversible and isothermal.
0. Just expansion. II. (6 points). Given the fOIIOWing reactiom:
CzHe(Q) "’r‘ 7/2 02(9) ”3% 2$0263) + 3H200)
202H2(g) + 5632(g) ”1% 4C02(g) + 2 H20“)
H2(g) + 1/2 02(9) u§ H200) CHMQ) 4" 202<9> ”9 002(9) + 2 H200) 02H4(9) 4’ 302(9) “”> 2 632(9) "’9“ 2 F4200) AH AH" AH” AH" AH° Calculate AH°f0r: (32H4(g) 4— 2 {42(9) w§ 2C3H4(g) ° 3 H1550 N K ~2599 RJ 3 £88 M E ~890 K) 2 4364 M .x‘ f w 2;} ‘ {a k 45 {{E A (“Q x V: (L, :1
{:3 ,2 Ekikg {: _ § 5‘: E) Q; (“N a :1:£3 I} ~ V) @iw K” a) E, Ci 1: y 0’ ,,
V A“ \ k hf
“' If ”t 53?” \
r? (.99 {N g? Y; /1 f” {5 mm};
‘ t»: g” 0 L“; V Q «x {f é; E “”5? Egg“ WC} """ k”) (k "I g
#k '3 Qt K g of r m“ (j
. , ; m. If M gm “x
\ H xx mgvg‘rgxbf’ﬂg g “{5} U“? «2": k§ygi§é}}
jévgé,.,%\;g iiﬁﬁgﬂéij/E """"""""" ; jugJr 4»; a!
y f f ........ X \
w f’ v~ x g \ 2 ~ \ L; k .y a
{a3 {g E <%X} ,3? f)“ Egajk k2? f 3' k} kw <§c€ E) w!) 1} 1C ,,,,,, J K,r Y’f ...... gag? /
“ E/%
E a Ui/j Ill. (12 points). An ice cube with a mass of 20 g at —20°C (typical freezer temperature) is
dropped into a cup that holds 500 mL of hot water, initially at 83"C. What is final temperature in
the cup? The density of liquid water is 1.00 g/mL; the specific heat capacity of ice is 2.03 J/g°C;
the specific heat capacity of liquid water is 4.184 J/g°C; the enthalpy of fusion of water is 6.01 kJ/mol. You MUST WET FULL CREDlT.
CD 7
r? a .
6) VJ‘ Va/l'v Tiuyq’ 83°C
(atm MW 7 m9. ~ aw. = m W W», M @
VIVW W Soul<4 0131*“ W 09"?
8w m W
£¢ MCJ AT’ ®
amc‘
l
PM W at W
”Md” toJ’r‘ ‘95 but“ Lye'4‘, Kym
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‘ ‘5 a
’ Lr ,. " 2 J. )(JrO'Sj 0. («“0 '
_ (9W 53(1 lf‘t%£§('l‘p 8’5 g) (C 06‘ (”CK 0 a0 a)
l
G) ’r (,‘othwml>(3°%)(ii°ij>
———"' ‘43
Moi W a) + (9,053mxw’93 >0; —oL\ "C
WJ‘W'L» [74%
J A w w
49.04;” + n'slm. I 2 a). + 92,7819 + mm; ~O uptown, 2 1H?!“ T; IV. (15 points) Short answer. (a) Explain why Brz is a liquid at room temperature and room pressure, but Cl; is a gas.
(Sr; W 5W W
cry bcm (Jr a {W K W
mar“ (34>wa _ (b) Can the entropy of the universe ever decrease? Explain. [Loka W {AA/Fur“ WM> ?. SQmW/J} QR Kirc‘ M D8 1‘. (c) Pick your favorite Law of Thermodynamics and describe it. lit/Au”. inwiwugﬂ boys/HQ sm’rpﬁww WM, V3 Lam' W3 4, M (sum swig» cum/m cl‘w‘yvn—e
W “K A 5PMWM 5”ij Woéawejorrﬂ «condo. (cl) Explain what a state function is — and  Give an example of something that IS a state
function and also an example of something that is NOT a state function. {’V shit Mann is a (9M 4 ASLpWJ/lwt” 1‘;
W {1/ka "it (3ng (W pro/(“two W”) 4 Wk) owe, stvk hast/NM‘ a)!” any s+vl< Max‘mm. (e) In what situations would you use the following equation: w = ~nRT In (VfNi)? ‘7“ LﬁecpJ/K WML (10%.. RM (“H—meg regentL/L/ ___/q .gypngw Waihba 0‘; N {AeM 9&5‘
/ 7 ...
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