Chem 2000B Quiz 1 (B)
Jan 21th, 2003: 11:35 am to 12.05 pm
Your name _______________
Instructor: Dr. P. Hazendonk
Student ID _______________
Time: 30 min
No. of pages: 4
Report all your answers using significant figures. Show all units and their conversions throughout your
calculations.
Question 1 (5 Marks)
Which compounds do you expect to dissolve in H2O? Explain your answer briefly in terms of the
intermolecular forces present.
(a) MgCl2
Ionic solid, dissociates into Mg2+ and Cl- ions, which are hydrated by water due to ion-dipole
interactions
(b) methylamine (NH2CH3)
methylamine contains H-bonds and hence undergoes hydrogen bonding with water and
hence is very soluble in water.
(c) pentane (C5H12)
Pentane is a non-polar liquid, hence it is immiscible with water.
(d) He
Argon is not very polarizable, and hence doesn’t not undergo strong dispersion forces with
water, hence is insoluble in water
(e) SiO2
SiO2 is a network solid, which was extremely strong lattice forces, which cannot be overcome
by solvent-solute interactions with water, and hence is insoluble in water.
Question 2 (5 Marks)
State whether the following statements are true or false.
i)
The boiling point of a liquid is the temperature at which its vapor pressure is equal to the
external pressure.
True
1
ii)
A volatile liquid has a high boiling point.
False
ii)
The stronger the intermolecular forces, the higher would be the boiling point.
True
iii)
The vapor pressure above a liquid increases with temperature.
True
iv)
The equilibrium vapor pressure above a liquid is dependent of the volume of liquid
present and the volume of the vapor present.
False
Question 3 (5 Marks)
Place the following sets of compounds in order of decreasing boiling point. Justify you answer in terms
of the relative strengths of intermolecular forces present.
i)
H2O and H2S.
H2O > H2S
since H2O undergoes hydrogen bonding, and H2S does not.
ii)
HI, HCl, and HBr.
HI > HBr > HCl
Dispersion forces increase with number of electrons, dipole forces increase with increasing
electronegativity difference. However dispersion forces dominate hence the boiling point
increases with molecular weight.
iii)
CI4, CF4, CBr4, or CCl4.
CI4 > CBr4 > CCl4 > CF4
These are non-polar molecules that undergo dispersion forces. As dispersion forces increase
with increasing number of electrons the boiling points increase accordingly.
2
Question 4 (5 Marks)
The Henry’s law constant for O2 in water at 28 oC is 1.83*10-6 M/mm Hg. What partial pressure of O2 , in
Pa, is required to achieve an equilibrium concentration of 0.250 M?
S = kh P
S/kh = P = (0.250 M)/(1.83*10-6 M/mm Hg) = (1.37*105 mm Hg)
=(1.37*105 mm Hg)/ (760 mm Hg/atm) (101325 Pa/atm) =1.82 * 10 7 Pa.
Question 5 (5 Marks)
The vapor pressure of water at 30 oC is 28.8mmHg. If 550 mL of water is placed in a chamber with
volume of 2.50 m3, how many litres of water will evaporate? (Assume that the density of water is 1.00
g/ml)
PV=nRT, P = 28.8 mm Hg,
V = 2.50 m3, T = 28 oC
n = PV/RT
= (28.8 mm Hg/760 mm Hg/atm)(2.50 m3)(1000 L/m3)/((0.0821 L atm mol-1)(273.15 + 28 K))
n = 3.832 mol
mass H2O = (3.832 mol H2O)(18.02 g/mol) = 69.0 g
Volume H2O = (69.0 g)/ ((1.00 g/ml)(1000 ml/L)) = 0.069 L
3
Fundamental Constants
Planck's constant, h 6.626 × 10-34 J s
Avogadro's number 6.022 × 1023 mol-1
Elementary charge (e) 1.6022 × 10-19 C
Electron mass
9.1095 × 10-28 g
Gas constant
8.314 J K-1mol-1
0.0821 L atm mol-1
pV = nRT
0
p solv = X solv ⋅ p solv
Rydberg Constant
Proton mass
Neutron mass
Speed of light in vacuum, C
1.097 x 107 m-1
1.67252 × 10-24 g
1.6749 × 10-24 g
2.998 x 108 m s-1
S g = K H ⋅ pg
Physical quantity
Unit
Symbol
Definition
Frequency, f or ν
Energy , W or E
Force, F
Pressure, p
hertz
joule
newton
pascal
Hz
J
N
Pa
s-1
kg m2 s-2
J m-1 = kg m s-2
N m-2 = kg m-1 s-2
Temperature: 0 K = -273.15 °C; 0 °C = 273.15 K
Pressure: 1 atm = 760 Torr = 760 mmHg = 1.01325 bar = 101325 Pa; 1 bar = 105 Pa
Volume: 1 mL = 1 cm3; 1 L = 1000 cm3 = 1 dm3 = 0.001 m3
1
Chem 1000 Standard Periodic Table
18
1.0079
1H
4.0026
2
13
14
6.941
9.0122
10.811
12.011
3Li
4Be
5B
6C
carbon
28.0855
nitrogen
30.9738
13Al
14Si
15P
16S
phosphorus sulfur
hydrogen
lithium
22.9898
berrylium
24.3050
11Na
boron
26.9815
sodium
39.0983
12Mg
magnesium
3
4
5
6
7
8
9
10
11
12
40.078
44.9559
47.88
50.9415
51.9961
54.9380
55.847
58.9332
58.693
63.546
65.39
aluminum silicon
69.723
72.61
19K
20Ca
21Sc
22Ti
23V
24Cr
25Mn
26Fe
27Co
30Zn
31Ga
potassium calcium
85.4678 87.62
scandium titanium
88.9059 91.224
vanadium chromium manganese iron
(98)
101.07
92.9064 95.94
79Au
80Hg
mercury
thallium
81Tl
82Pb
lead
bismuth
157.25
158.925
162.50
164.930
167.26
186.207
55Cs
La-Lu
cesium
(223)
56Ba
barium
226.025
72Hf
73Ta
74W
75Re
76Os
87Fr
88Ra
Ac-Lr
104Rf
105Db
dubnium seaborgium bohrium
106Sg
107Bh
144.24
(145)
140.115
140.908
59Pr
89Ac
90Th
lanthanum cerium
227.028 232.038
actinium9 thorium
32Ge
33As
germanium arsenic
78Pt
183.85
ruthenium rhodium
190.2
192.22
58Ce
77Ir
osmium
(265)
iridium
(266)
hassium
108Hs
109Mt
meitnerium
150.36
151.965
platinum gold
48Cd
49In
18Ar
78.96
argon
83.80
34Se
35Br
36Kr
51Sb
52Te
53I
84Po
85At
168.934
173.04
174.967
69Tm
thulium
(258)
70Yb
ytterbium lutetium
(260)
(259)
71Lu
101Md
102No
103Lr
238.029
237.048
(240)
(243)
(247)
(247)
(251)
92U
93Np
94Pu
95Am
96Cm
97Bk
4
17Cl
chlorine
79.904
50Sn
91Pa
neptunium plutonium americium curium
neon
39.948
121.757
231.036
uranium
fluorine
35.4527
118.710
66Dy
67Ho
68Er
dysprosium holmium erbium
(252)
oxygen
32.066
selenium bromine
127.60
126.905
60Nd
61Pm
62Sm
63Eu
64Gd
65Tb
praesodymium neodymium promethium samarium europium gadolinium terbium
protactinium
74.9216
tin
207.19
43Tc
138.906
10Ne
cadmium indium
200.59
204.383
42Mo
57La
20.1797
9F
47Ag
41Nb
rutherfordium
18.9984
palladium silver
195.08
196.967
zirconium niobium
178.49
180.948
francium radium
15.9994
8O
46Pd
40Zr
rhenium
(262)
14.0067
7N
45Rh
39Y
gallium
114.82
helium
copper
107.868
38Sr
zinc
112.411
17
nickel
106.42
37Rb
hafnnium tantalum tungsten
(261)
(262)
(263)
44Ru
29Cu
(257)
98Cf
99Es
100Fm
berkelium californium einsteinium fermium
2He
16
cobalt
102.906
rubidium strontium yttrium
132.905 137.327
molybdenum technetium
28Ni
15
antimony tellurium iodine
208.980 (210)
(210)
83Bi
polonium astatine
mendelevium nobelium lawrencium
krypton
131.29
54Xe
xenon
(222)
88Rn
radon