Chem 1000B Midterm 1 – Fall 2003 - Solutions
A
Oct 1st , 2003: 11:00 to 11.50 am
Your name _______________
Instructor: Dr. M. Gerken
Student ID _______________
Time: 50 min
No. of pages: 4
Report all your answers using significant figures. Show all units and their conversions throughout your
calculations.
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Total Percent
3
5
3
5
8
8
5
6
43
100 %
Question 1 (3 Marks)
Give the formula for each of the following ionic compounds:
(a) potassium hydrogen sulfate
_____KHSO4_____________________________
(b) barium chloride
_____BaCl2_______________________________
(c) ammonium hydroxide
_____NH4OH_____________________________
Question 2 (5 Marks)
Complete the following table.
Isotope
195
Pt2+
209
Bi3+_
Number of electrons
76_
80
Number of neutrons
117_
126
Number of protons
78_
83_
Overall charge
2+
3+
Question 3 (3 Marks)
Carry out the following calculation, and report the answer in the correct number of significant figures and
scientific notation.
8.300 g ×0.800 kg – 18.02 g3/3.00 mg
8.300 g×0.800 kg– 18.02 g3/3.00 mg =8.300 g ×800. g – 18.02 g3/0.00300 g
=6640 g2 -6010 g2 =630 g2 =6.3 × 102 g2
1
Question 4 (5 Marks)
What is the mass of
(a) one P4 molecule (in u)
123.8952 u
(b) one mol of P4 molecules (in g and u)
123.8952 g
6.022 × 1023 u = 1 g
123.8952 g × (6.022 × 1023 u/1 g) = 7.461 × 1025 u
(c) one mol of P atoms (in g)
30.9738 g
Question 5 (8 Marks)
Draw the Lewis structure of the following compounds (central atom is underlined) and determine the
oxidation states of all atoms in these compounds.
(a) ClOCl
.. ..
.. O ..
: Cl
Cl
.. :
..
oxidation states: O: -II, Cl:+I
(b) FOF
.. ..
.. O ..
: ..F
F
.. :
oxidation states: O: +II; F: -1
(c) NO2
.+
N
:O
.. : O
.. : _
.
N+
_:O
.. : O
.. :
oxidation states: N: +IV; O: -II
2
Name _________________________
Student ID _________________
Question 6 (8 Marks)
A compounds has the percent composition of 0.740 % H, 28.713 % K, 46.998 % O, and 23.549 % S.
(a) Determine the empirical formula of this compound.
100 g of the compounds contains: 0.740 g H, 28.713 g K, 46.998 g O, and 23.549 g S
moles H: n(H) = 0.740 g H / (1.0079 g H/ mol H) = 0.734 mol H
moles K: n(K) = 28.713 g K / (39.0983 g K/ mol K) = 0.73438 mol K
moles O: n(O) = 46.998 g O / (15.9994 g O/ mol O) = 2.9375 mol O
moles S: n(S) = 23.549 g S / (32.066 g S/ mol S) = 0.73439 mol S
n(H) : n(K) : n(O) : n(S) = 0.734 : 0.73438 : 2.9375 : 0.73439
= 1 : 1.001 : 4.002 :1.001
≈1:1:4:1
empirical formula: HKO4S
(b) The molar mass of this compound was experimentally determined as 136.17 g/mol. What is the
molecular formula of the compound.
M(HKO4S) = 136.170 g/mol
Molecular formula: HKO4S = KHSO4
M(HKO4S)/ 136.17 g/mol ≈ 1
(c) Name the compound.
Potassium hydrogen sulfate
Question 7 (5 Marks)
Thallium is composed of two isotopes,
203
Tl and
205
Tl. The isotopes
203
Tl and
abundances of 29.524 % and 70.476 %, respectively. The isotopic mass of
Determine the isotopic mass of the 205Tl isotope.
203
Tl
202.972335 u
0.29524
205
Tl
x
0.70476
Tl (average)
204.383 u
1
202.972335 u × 0.29524 + x × 0.70476 = 204.383 u
59.926 u + x × 0.70476 = 204.383 u
x × 0.70476 = 144.457 u
x = 204.97 u (isotopic mass of 205Tl)
3
203
205
Tl have isotopic
Tl is 202.972335 u.
Question 8 (6 Marks)
(a) Draw the Lewis structure of PCl3. (b) Specify the electron-pair geometry and the molecular geometry
of PCl3 according to the VSEPR model. (c) What value do you expect for the Cl-P-Cl angle? (d) Is PCl3
polar? Indicate the molecular dipole moment in the case PCl3 is polar.
(a)
..
.. P
:Cl
..:Cl : :Cl :
..
..
_
(b) electron-pair geometry: tetrahedral
molecular geometry: trigonal pyramidal
(c) The Cl-P-Cl angle should be smaller than 109.5 (the angle in a perfect tetrahedron) since the long
pair – bonding pair repulsion is larger than the bond pair- bond pair repulsion.
(d) PCl3 is a polar molecule.
Prefixes
Pico, p 10-12; nano, n 10-9; micro, µ 10-6 ;milli, m 10-3; centi, c 10-2; deci, d 10-1
Fundamental Constants
Avogadro's number 6.022 × 1023 mol-1
Proton mass
1.67252 × 10-24 g
Neutron mass
1.6749 × 10-24 g
Elementary charge, e 1.6022 × 10-19 C
m
m
Electron mass
9.1095 × 10-28 g
ρ=
n=
V
M
4
Physical quantity
Unit
Symbol
Definition
Frequency, f or ν
hertz
Hz
s-1
Energy , W or E
joule
J
kg m2 s-2
Force, F
newton
N
J m-1 = kg m s-2
Pressure, p
pascal
Pa
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
Electronegativities
18
2.1
H
1
1.0
Li
3
1.0
Na
11
0.9
K
19
0.9
Rb
37
0.8
Cs
55
0.8
Fr
87
2
13
1.5
2.0
Be
5
1.5
Mg
Ca
20
1.0
3
1.3
Ba
56
1.0
Ra
88
4
1.4
Sc
21
1.2
Sr
38
1.0
2.5
B
4
1.2
12
1.0
14
Y
39
1.1
La
57
1.1
5
1.5
Ti
22
1.3
V
23
1.5
Zr
40
1.3
Nb
41
1.4
Hf
72
Ta
73
6
1.6
Cr
24
1.6
Mo
42
1.5
W
74
7
1.6
Mn
25
1.7
Tc
43
1.7
Re
75
8
1.7
Fe
26
1.8
Ru
44
1.9
9
1.7
1.8
Co
Ni
27
1.8
28
1.8
Rh
Pd
45
1.9
Os
76
10
46
1.8
Ir
Pt
77
78
11
1.8
Cu
29
1.6
Ag
47
1.9
Au
79
12
1.6
Zn
30
1.6
Ga
31
1.6
Cd
48
1.7
In
49
1.6
Hg
80
Tl
81
3.0
C
6
1.8
Al
13
1.7
15
Ge
32
1.8
Sn
50
1.7
7
2.1
As
33
1.9
Sb
51
1.8
Bi
83
17
8
2.5
F
9
3.0
S
16
2.4
Se
34
2.1
Cl
17
2.8
Po
84
Ar
18
2.9
Br
35
2.5
Te
52
1.9
Ne
10
3.3
Kr
36
2.3
I
53
2.1
At
85
Xe
54
Rn
86
Ac
89
1
Chem 1000 Standard Periodic Table
18
1.0079
1H
He
2
4.0
O
P
15
2.1
Pb
82
3.5
N
Si
14
1.9
16
4.0026
2He
hydrogen
2
13
14
15
16
17
helium
6.941
9.0122
10.811
12.011
14.0067
15.9994
18.9984
20.1797
3Li
4Be
5B
6C
7N
8O
9F
10Ne
11Na
12Mg
lithium berrylium
22.9898 24.3050
boron
26.9815
3
4
5
6
7
8
9
10
11
12
47.88
50.9415
51.9961
54.9380
55.847
58.9332
58.693
63.546
65.39
21Sc
22Ti
23V
24Cr
25Mn
26Fe
29Cu
30Zn
39Y
40Zr
41Nb
42Mo
43Tc
44Ru
72Hf
73Ta
74W
sodium magnesium
39.0983 40.078 44.9559
19K
20Ca
37Rb
38Sr
55Cs
56Ba
La-Lu
88Ra
Ac-Lr
potassium calcium scandium titanium vanadium chromium manganese
iron
85.4678
(98)
101.07
87.62
88.9059 91.224 92.9064
95.94
rubidium strontium
132.905 137.327
cesium
(223)
87Fr
francium
yttrium zirconium niobium
178.49 180.948
barium
226.025
molybdenum technetium
183.85
hafnnium tantalum tungsten
(261)
(263)
(262)
104Rf
rutherfordium
radium
zinc
112.411
45Rh
46Pd
47Ag
48Cd
75Re
rhenium
(262)
76Os
78Pt
79Au
77Ir
osmium
(265)
iridium
(266)
107Bh
hassium meitnerium
108Hs
109Mt
144.24
(145)
150.36
151.965
140.908
58Ce
59Pr
89Ac
90Th
platinum
(269)
15P
phosphorus
31Ga
32Ge
49In
50Sn
16S
fluorine
35.4527
neon
39.948
17Cl
18Ar
74.9216
sulfur
78.96
chlorine
79.904
33As
34Se
35Br
51Sb
52Te
83Bi
gallium germanium arsenic selenium bromine
114.82 118.710 121.757 127.60 126.905
tin
207.19
antimony tellurium
208.980
(210)
53I
85At
88Rn
81Tl
82Pb
158.925
162.50
164.930
167.26
168.934
173.04
174.967
66Dy
67Ho
dysprosium holmium
68Er
69Tm
70Yb
71Lu
65Tb
231.036
238.029
237.048
(240)
(243)
(247)
91Pa
92U
93Np
94Pu
95Am
96Cm
97Bk
uranium neptunium plutonium americium curium
(251)
(252)
erbium
(257)
54Xe
84Po
thallium
bismuth polonium astatine
110Ds
157.25
36Kr
krypton
131.29
xenon
(222)
mercury
lead
argon
83.80
iodine
(210)
gold
terbium
(247)
5
14Si
silicon
72.61
oxygen
32.066
darmstadtium
60Nd
61Pm
62Sm
63Eu
64Gd
praesodymium neodymium promethium samarium europium gadolinium
protactinium
80Hg
nitrogen
30.9738
aluminum
69.723
ruthenium rhodium palladium silver cadmium indium
186.207
190.2
192.22
195.08 196.967 200.59 204.383
106Sg
140.115
actinium9 thorium
copper
107.868
105Db
57La
28Ni
nickel
106.42
dubnium seaborgium bohrium
138.906
lanthanum cerium
227.028 232.038
27Co
cobalt
102.906
13Al
carbon
28.0855
thulium ytterbium lutetium
(258)
(260)
(259)
98Cf
99Es
100Fm 101Md
102No
103Lr
berkelium californium einsteinium fermium mendelevium nobelium lawrencium
radon