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[CHY102] CHY102 Midterm #2 2007 Test + Solutions

Ryerson University
Uploaded: 3 months ago
Contributor: bolbol
Category: Chemistry
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Filename:   [CHY102] CHY102 Midterm #2 2007 Test + Solutions (1).pdf (2.06 MB)
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:Enter All Answen in the Scantron Sheets
' MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the
question.
1) The reaction
PCI5(g) ~ PCI3(g) + CI2(g)
has a value ofKp of 110 at 760 K. If the initial pressure of PCI5 is 2.40 atm, what is the pressure
of PCl3 at equilibrium? Ptl~ <2- f O ~ .._ O·i
A) 22.2 atm 1 l.."lo 0 0
~---:. )o... i>--- -1'"'",i..
J?J_).18 atm
~.35 atm
D) 2.42 atm
I..
1- bq_ - '\ @)(...; "f- - i,b rA
i.. 'l"'\\Dx I) -::0 Yi-. = '}_ .3 "\
2) How does the kinetic molecular theory of gases explain the relationship between pressure and
temperature?
~ At higher temperatures, the molecules have more energy. When they run into the walls, they
""- ~sfer less of the energy to the walls. .
~ higher temperatures, the molecules have more energy and run into each other more often,
,,_ increasing the pressure. ··
t}At a higher temperature, the molecules collide with the walls more often and with more ·
force, increasing the pressure.
D) At higher temperatures, there are more collisions with the walls, but each collision transfers
less energy.
la_(J'L
3) Calcium chloride is an ionic compound that readily dissolves in water. What is the vapor pressure
ofa solution of8.45 grams of calcium chloride dissolved in 376 grams of water at l00°C?
@57 mmHg f)_ ~ ,._ 2,o...... ...-.I\ .•
B) 98.9 mmHg () D ....u
C) 752 mmHg ~<;... ~ {k p .._0
c .01~ ""1\
D) 91.3 mmHg
1
Enter All Answen in the Scantron Sheets
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answen the
question.
1) The reaction
PCl5(g) ~ PCl3(g) + Cl2(g)
has a value ofKp of 110 at 760 K. If the initial pressure of PCl5 is 2.40 atm, what is the pressure
ofPCl3 at equilibrium? Pct~~ fO.,,.,, C..\'l.
A) 22.2 atm -e'~~ 0
~r- : ...
.18atm e 2 ..... o-c1-
.35 atm
D) 2.42 atm
I..
tb~ - '\@)(..; f- - 'l)i~ i.. 1-'\\D >< I) -:;; Yi-...: '}_ $'"'\
2) How does the kinetic molecular theory of gases explain the relationship between pressure and
temperature?
~ At higher temperatures, the molecules have more energy. When they run into the walls, they
""- ~sfer less of the energy to the walls. .
~ higher temperatures, the molecules have more energy and run into each other more often,
creasing the pressure. --
t}At a higher temperature, the molecules collide with the walls more often and with more ·
force, increasing the pressure.
D) At higher temperatures, there are more collisions with the walls, but each collision transfers
less energy.
la.(j._'L
3) Calcium chloride is an ionic compound that readily dissolves in water. What is the vapor pressure
of a solution of 8.45 grams of calcium chloride dissolved in 376 grams of water at 100°C?
@757 mmHg 2 ~ -- 2,o,""- .,;J\._.
B) 98.9 mmHg () 0 ..µ
C) 752 mmHg ~ .;_ :r {k P.__0
o .016 f,.;J\
D) 91.3 mmHg
1
Enter All'Answers in the Scantron Sheets
4) What is the strongest intermolecular force present in the in the molecule acetone, (CH3)2C=O?
A) London dispersion forces
B) Dipole-dipole attractions
C) Hydrogen bonds
D) Covalent bonds
5) The reaction
H2(g) + Cl2(g) ~ 2HCl(g)
has an equilibrium constant of 4.0 x 1 Q31. What is the equilibrium constant for the reaction
1 1 HCl(g) ~ - H2(g) + - Cl2(g)? 2 2
A) 6.3 x 1015 <l
B) 2.5 x 10-32 .,,, •
C) 6.3 x 10-16
DJ .6 x 10-16 ,
6) Carbon tetrachloride has a normal boiling point of 76.8°C and an enthalpy of vaporization of29.8
kJ/mol. What is the vapor pressure of carbon tetrachloride at 25°C?
A) 128 mmHg /'
B) 910 mmHg --1i-'°
IL,.{"' C) 634 mmHg ·-=>
D)690mmHg
7) The crystal structure of argon was measured at low temperatures. Argon crystallizes in a
face-centered cubic unit cell with an edge of 525.6 pm. What is the density of argon at this
temperature?
A) 1.827 g/cm~
B) 7.600 g/cm3
C) 0.4569 g/cm3
D) 0.9137 g/crn3
2
f
Enter All Answen in the Scantron Sheets
8) Why do ionic solids have a high melting point and a large L:..Hfus?
A) The dipole-dipole attractions and London dispersion forces are very strong.
fil.. The covalent bonds that hold the solid together are difficult to break.
c£))The attractions between the positive and negative ions are very strong.
D) The ions are not stabilized very well in the liquid phase.
9) A gas sample has the following partial pressures: P(02) = 234 mmHg, P(N2) = 579 mmHg, and
P(H 20) = 36.3 mmHg. What is the mole fraction of water in the gas mixture?
A) 0.043
B) 0.059
C) 0.063
D) 0.045
10) If~~ has a pressure of 0.873 atm at l 96°C, what is its pressure at 37.2°C?
(b}-0.577 atmospheres n~ l
B) 0.422 atmospheres £ -h J.-\ .. U-z 1 \__,,......
D)
C)
0.217
1.68 atmospheres
atmospheres
~. ~ ~
- p f
:::-- ? T -
11) One method used to measure the volume of an irregularly shaped container is to fill it with a
known mass of gas and measure the pressure and temperature of the gas. A mass of 3 .679 grams of
02 gas is added to the container at 3 7 .2°C causing the container to develop a pressure of 493 torr.
What is the volume of the container?
~ 1.90 liters
(ID)4.52 liters
C) 0.00595 liters
D) 0.542 liters
3
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Use the diagram in Figure 1 for the question that follows
Phase Diagram for a Hypothetical Substance
b rd 1
p a. / m
e ------------------- ·--- ------ __________ k _ _( _____________________________ ___________ 1-.0 atm.
s
s
u
e
g f
h c
e
Temperature
Figure L A phase diagram for a hypothetical substance
12) What is represented by the point e on the diagram in Figure 1?
~Critical point
@D'riple point
C) Normal boiling point
D) Melting point
13) Sodium crystallizes in a body-centered cubic unit cell. How many atoms are contained in the unit
cell of sodium? ©2
B) 1
C)4
D)9
14) The density of a 10% solution of sulfuric acid in water is 1.0687 g/rnl. What is the molarity of this
solution?
W 0.955M
B) 1.09M IL
C) 5.94 M
D) 1.07 M
4
Enter All Answen in the Scantron Sheets
15) Consider the reaction
CO(g) + H20(g) ~ C02(g) + H2(g).
Which of the following initial compositions will NOT achieve equilibrium?
A) 0.25 mol H2, 0.35 mol C02, and 0.25 mol CO
B) 0.25 mol CO and 0.75 mol H20
C) 1.0 mol of C02 and 0.50 mol H2
D) 0.85 mol CO and 0.25 mol H2
16) The equilibrium constant for the reaction
2NOCl(g) ~ 2NO(g) + Cl2(g) is 3.9 x 10-3 at 300°C.
A mixture of gases has the following composition: [NOCl] = 5.0 x 1 o-3 mol/L, [NO] = 2.5 x I o-3
mol/L, and [Cl2] = 2.0 x 1o-3. Is the system at equilibrium? If not, in which direction should the
re~· on go to achieve equilibrium?
A) o, reactants will be converted to products.
) Yes, equilibrium has been achieved.
C) No, products will be converted to reactants.
D) No, equilibrium cannot be achieved.
17) Th~ of water at 50°C is 5 .4 7 x 10-14. What is the pH of pure water at 50°C?
A) .63
7.00 t -s {
C) 7.37
@ 13.3
18) What force holds the metal atoms together in a metallic solid?
AJ-Tue metal atoms either lose electrons or gain electrons to form ions to hold the crystal
together.
~ondon dispersion forces hold the atoms together in the crystal structure.
'C:::~ Valence electrons are delocalized throughout the crystal, generating a strong cohesive force.
D) Valence electrons form a series of covalent bonds that hold the crystal together.
5
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19) Consider titration of 25.00mlof0.200 M acetic acid with 0.100 M sodium hydroxide. What is the
· concentration of acetate ion when 30.00 ml of sodium hydroxide has been added?
A) 0.0909 M -
B) 0.0364 M
C) 0.0545 M
D) 0.0800 M
20) The normal freezing point of cyclohexene is 6.55°C. When 0.458 grams ofbenzophenone is
dissolved in 15.0 grams of cyclohexene, the freezing point is found to be 3. l 9°C. What is the
experimental molar mass of benzophenone? Kffor cyclohexene is 20.0°C/m.
A) 182 g/mol
B) 866 g/mol
C) 397 g/mol
D) 191 g/mol
2 I) Why is the pH of a 0.1 M solution of sodium acetate not equal to 7?
A) The acetate ion reacts with water to release hydroxide ions, making the solution basic.
B) The sodium ion reacts with water to release hydroxide ions, making the solution basic.
C) The sodium ion reacts with water to release hydrogen ions, making the solution acidic.
D) The acetate ion reacts with water to release hydrogen ions, making the solution acidic.
22) A pH 4.74 buffer is prepared by adding 0.100 moles of sodium acetate to O.l 00 moles of acetic
acid and diluting to 1.00 liters. What is the pH of the solution after the addition of 5.00 ml of I .00
M hydrochloric acid?
~
B) 4.70
C) 4.72
D) 3.44
6
Enter AB.Answers in the Scantron Sheets
23) How much energy is required to take 150 g of ice at -10°C and convert it to water at 3 7°C?
Remember, specific heat of water = 4.184 J/g°C, .6.Hfus = 6.01 kJ/mol, and specific heat of ice =
2.09 J/g°C.
A) 51.5 kJ
B) 76.4 kJ
C) 27.3 kJ
D) 928 kJ
24) What type of interaction is responsible when a nonpolar solute does NOT dissolve in a polar
solvent?
A) The energy required to separate the solute molecules is too large to be made up by
solvent-solute interactions.
B) The solvent-solute interactions cannot overcome the strong solute-solute interactions in
order to separate the solute.
C) The polar solvent repels the nonpolar solute molecules, which makes it impossible for a
solution to form.
D) The separation of the solvent molecules requires more energy than can be recovered from
solvent-solute interactions.
7
Equations Chapter 15
aA + bB <=> cC + dD
Equations Chapter 16
pH = - log[W]
[H. ][A- ] x 2
K = [HA] = (CHA - x)
pH + pOH = pK.,
[CY[Dt
Q= [A]
0 [Bt
(
base) pH = pKa + log acid
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1A 2A 38 48 58. 68 78 8B 88 es 18 28 3A CA 5A 6A 7A &A
-1 ~
H He
1.008 4.003
3 4 5 6 7 8 9 10
2 Li Be B c N 0 F Ne
6..941 9.012 - 10.81 12.01 14.01 16.00 18.99 20.18
11 12 13 14 15 16 17 18
3 Na Mg Al Si p s Cl Ar
22.99 24.30 26.98 28.0S 30.tl7 32.07 35.445 39.95
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
A K Ca Sc Ti v Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
39.10 14o.oe 44.96 147.87 50.94 52.00 SUM 55.IM 58.99 58.34 63.55 65.39 69.n 72.81 74.92 i18.96 79.90 83.8
37 38 39 40 41 42 43 "' 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 as.47 87.62 88.91 91.22 92.91 94 99 101.1 102.9 106.4 107.9 112.A 114.8 118.7 121.8 127.6 126.9 131.3
55 56 57 n 73 74 75 76 17 78 79 80 81 82 83 84 85 86
6 Cs Ba La Hf Ta w Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
132.sl 137.3 138.9 178.5 181 .0 183.11 1116.2 190.2 192.2 195.1 197.0 6 204.A 207.2 209.0 209 210 222
87 88 89
7 Fr Ra Ac
223 226 227
58 59 60 81 62 63 64 65 e6 67 68 69 70 71
6 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
140.1 140.9 144.2 145 150 ... 152.0 157.2 158.9 162..5 164.9 167.3 168.9 173.0 175.0
90 91 92 93 94 95 96 97 98 99 100 101 102 103
7 Th Pa u Np Pu Am Cu Bk Cf Es Fm Md No Lr
232.1 1231 .0 238.0 237 244 243 247 247 251 252 257 258 259 262
useful constants and conversions:
1 amu = 1.66054 x 10-24 g
gas constant R= 8.314 J/mol·K = 0.0821 L·atm/mol·K
Avogadro's number Na = 6.022 x 10 23
ion-product constant Kw = 1.0 x 10-14 at 25 °C
F-araday2-s-ronstant F = 9.(:)486 x lh(V*mol)
standard temperature and pressure STP = 1 atm, 0 ° C
room temperature and pressure RTP = 1 atm, 25 ° C
0° C = 273 K
1atm=760 torr = 760 mm Hg= 101325 Pa
Equations Chapter 1-4
m
n=-- n M =-
V
mass sample actual I r 0 J J.: -lo 3 [ Ir) -]
mass%= l x 100% % y ield= . h x 100%
M w Tota mass t eor.
pH = - log[H+]
L~qua~onsChap~ E = - mv2 6 U = U - U k 2 final initial 6U=q+w /),_ H = H final - H,mua/ = q rxn
q = nCm 6 T q = Ccai 6 T q = ms6 T = me_, 6 T
6H:n =I n6~(products)- I m6H (reactants)
Equations C~apters G
F
P=-
A
PV= nRT
T-r 7 .
(
mass of component in sol' n 9 ppb= xlO total mass s
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