School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
External Examiner: Dr Colin Southway
University of KwaZulu-Natal
Pietermaritzburg
Internal Examiners: R Moodley
S Chellakootty
R Robb
UKZN – Westville
M Rasalanavho
A van der Hoven
UKZN – Pietermaritzburg
Duration: 3 Hours
Total Marks: 100
Instructions to Candidates:
•
Answer all 5 questions on the paper provided and show your working clearly.
•
Marks are given in brackets after each part-question and all questions are
marked out of 20.
•
The question paper consists of 11 pages including a Periodic Table, a Data
Sheet and Electronegativity values
•
Please check that you have them all.
Page 1 of 11
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
Question 1 [20 marks]
1.1
Redraw the following concept map on mole calculations, correcting any
equations that are incorrect. Use ALL the phrases that are provided. Each
phrase may only be used once.
Mass of a substance
Volume of solution
=
Number of moles
=
Volume of a gas x Number of particles
1.2
(4)
=
=
Molar mass
Avogadro's number
Concentration
Molar Volume
Hydrofluoric acid, HF(aq), cannot be stored in glass bottles because certain
compounds in glass react with HF(aq). Analysis of one of these compounds
showed that it contained 37.61 % sodium, 23.37 % silicon and the remainder
was oxygen.
a. Determine the empirical formula of the compound.
(5)
b. Apart from the type and number of atoms found in the compound,
what other information does the formula provide?
(1)
c. What experimental information is required so that one can determine
the molecular formula of this compound?
1.3
(1)
An unlabelled reagent bottle containing concentrated sulfuric acid (H2SO4) was
found in a student locker. A technician then accurately diluted 17.6 ml of the
concentrated sulfuric acid in a 1.50 dm3 container and carried out an analysis
to determine its concentration.
Page 2 of 11
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
a. Give a name of the container that the technician would use
to prepare the dilute solution.
(1)
b. Determine the concentration of sulfuric acid in the original bottle if the
concentration of the analyzed dilute solution was found to be 0.1350 M
H2SO4?
1.4
(4)
Calculate the mass of nitrogen in 3.674 g of NH4NO3.
(4)
Question 2 [20 marks]
2.1 4.89 L of chlorine (at 25 °C and 1 atm) was passed through a solution
containing excess sodium bromide. Which product is produced in the greatest
quantity (in grams)?
Cl2(g) + 2NaBr(aq)
→
Br2(g) + 2NaCl(aq)
[MM (Br2) = 159.80 g/mol and MM (NaCl) = 58.44 g/mol]
(5)
2.2 A 0.696 mole sample of copper was added to 0.136 L of 6.00 M nitric acid.
43.04 g of copper(II) nitrate, Cu(NO3)2, was produced, according to the
following equation:
3Cu(s) + 8HNO3(aq)
→
3Cu(NO3)2(aq) + 4H2O(l) + 2NO(g)
a. What mass of copper was added to nitric acid?
b. Determine which reagent is limiting.
Page 3 of 11
(1.5)
(3)
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
c. What mass of excess reagent remained on completion of the reaction?
(2.5)
d. What volume of gas was produced if the reaction was carried out at
25 °C and 1 atm?
(3)
e. What mass of copper(II) nitrate can be produced in the above
reaction?
(3)
f. Calculate the percentage yield of copper(II) nitrate.
(2)
Question 3 [20 marks]
3.1
Consider the metals in Group 1 and answer the following questions:
a. Give the general name for these elements.
(1)
b. Write out the Bohr electronic configuration for the element in
Period 3.
(1)
c. Draw the Lewis Electron Dot structure for the least reactive element. (1)
d. Write out the ground state spectroscopic electronic configuration
for the element in Period 5.
(1)
e. Draw the tabular electronic configuration for the element in Period 4 (1)
3.2
The following notations represent atoms and ions of different elements:
137
56
X 2+
,
X −138
127 −
,
I
a. Identify the element X.
(1)
b. Consider the number of subatomic particles and answer the following
questions:
137
X 2+
different from
X −138 ?
(i)
How is 56
(ii)
What is the term used to describe X-137 and X-138?
Page 4 of 11
(1)
(1)
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
(iii)
137
How is 56
X 2+ similar to
127 −
I
?
Give a reason for your answer.
3.3
(2)
An element has the following spectroscopic electronic configuration
1s22s22p63s23p64s23d104p1
a. Identify the element.
(1)
b. How many valence electrons does this element have?
(1)
c. Which energy sublevel has the highest energy?
(1)
d. How many orbitals are there in the highest energy sublevel?
(1)
e. Write out the abbreviated spectroscopic electronic configuration for
this element.
3.4
(1)
Choose expressions from the table provided which match with the general
electronic configurations given in a) to e) below.
NOTE:
•
An answer can be used more than once.
•
Some questions may have more than one answer, in which case, all
answers must be provided to obtain the mark.
Page 5 of 11
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
Transition elements f-block
Fluoride ion
Lanthanides
Hydrogen ion
Hydride ion
d-block
s-block
Helium
p-block
Argon
Halogens
a. ns1
b. ns2
c. ns2np5
d. ns2np6
e. ns2(n-1)d1-10
(5)
Question 4 [20 marks]
4.1 Read the following statements and correct all formulae that are incorrect.
a. The formula for ammonium dichromate is (NH4)2CrO4.
b. The formula for copper(II) nitrite is CuNO3.
c. The formula for germanium(IV) oxide is GaO.
(6)
4.2 Complete the following sentences. Write out the entire sentences in your
answer.
a. The following are examples of ions that are isoelectronic with argon:
two cations ………… & ………… and two anions ………… & …………… (2)
b. Electronegativity is ………………………………………………………………….. (1)
c. The halogens form ions by ………………….. electrons and the Group 2
elements form ions by …………………………..…. electrons. Therefore, in
general, the electronegativity of the halogens is …………..……… than
that of Group 2 elements.
Page 6 of 11
(1)
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
d. A polar covalent bond is one in which the electrons are shared……..…….
between two non-metallic atoms. Polar bonds are shown by the …………
notation which uses the symbols …………… and ……….…..
(2)
4.3 Study the following table of compounds, and then answer the questions that
follow.
NOTE:
•
Each formula can be used more than once in answering questions a to h
•
Write the full formula for each answer
•
Some questions may have more than one answer, and some may have
no answer, in which case say ‘none’ or ‘no answer’
•
Each question is worth one mark
•
The mark will be assigned only if the complete answer is given
NH4Cl
CH3CH2CH3
Cu2S
NH4OH
H3PO3(aq)
AlN
CaCO3
CO2
KCl(aq)
CH3COONa
BaF2
CuSO4.5H2O
a. Write down the formula(e) for all the substances which contain polyatomic
anions.
b. Write down the formula(e) for all the tri-atomic compounds
c. Write down the formula(e) for all the covalent compounds
d. Write down the formula(e) for all the compounds which are products of
combustion of hydrocarbons.
e. Write down the formula(e) for substances containing water
f. Write down the formula(e) for substances containing a +1 monoatomic cation
g. Write down the formula(e) for substances containing hydroxide ions
h. Write down the formula(e) for compounds containing an alkali element(s)
(8)
Page 7 of 11
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
Question 5 [20 marks]
Hydrated nickel(II) chloride crystals (NiCl2.nH2O) are green in colour. When heated
strongly they turn yellow. Three samples of this hydrated salt were weighed and
then heated for 5 minutes in a crucible over a Bunsen burner. The samples were
then cooled to room temperature in a desiccator and weighed again. This process
was repeated three more times. The data from the experiment was recorded in
the table below:
Sample mass (g)
Time
5.1
(minutes)
A
B
C
0
7.8331
7.8375
7.8406
5
5.0004
5.0091
5.0087
10
4.2724
5.0732
4.2795
15
4.2716
4.2742
4.2756
Using data from any sample, explain why this experiment is an example
of an open system.
(1)
5.2
What type(s) of reaction is occurring here?
(1)
5.3
What is the function of a desiccator?
(1)
5.4
Explain the purpose of heating and weighing several times. What is this
process called?
5.5
(2)
Use calculations to determine which experimental results are suitable for
determining the value of n in NiCl2.nH2O.
(4)
5.6
Calculate the value of n in the formula NiCl2.nH2O.
(4)
5.7
Write a balanced equation for the process, including state symbols.
(2)
5.8
Besides reading the mass balance incorrectly, list 2 other experimental
5.9
errors which could result in inaccurate mass readings.
(2)
Calculate the mass percentage of water in the hydrated compound.
(3)
Page 8 of 11
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
TABLE OF R
Page 9 of 11
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
RELATIVE ATOMIC MASSES (Based on Carbon-12)
Actinium
Aluminium
Americium
Antimony
Argon
Arsenic
Astatine
Barium
Berkelium
Beryllium
Bismuth
Boron
Bromine
Cadmium
Calcium
Californium
Carbon
Cerium
Cesium
Chlorine
Chromium
Cobalt
Copper
Curium
Dysprosium
Einsteinium
Erbium
Europium
Fermium
Fluorine
Francium
Gadolinium
Gallium
Germanium
Gold
Hafnium
Helium
Holmium
Hydrogen
Indium
Iodine
Iridium
Iron
Krypton
Lanthanum
Lawrencium
Lead
Lithium
Lutetium
Magnesium
Manganese
Mendelevium
Symbol
Ac
Al
Am
Sb
Ar
As
At
Ba
Bk
Be
Bi
B
Br
Cd
Ca
Cf
C
Ce
Cs
Cl
Cr
Co
Cu
Cm
Dy
Es
Er
Eu
Fm
F
Fr
Gd
Ga
Ge
Au
Hf
He
Ho
H
In
I
Ir
Fe
Kr
La
Lr
Pb
Li
Lu
Mg
Mn
Md
Atomic
number
89
13
95
51
18
33
85
56
97
4
83
5
35
48
20
98
6
58
55
17
24
27
29
96
66
99
68
63
100
9
87
64
31
32
79
72
2
67
1
49
53
77
26
36
57
103
82
3
71
12
25
101
Atomic
mass
[227]
26.98
[243]*
121.75
39.95
74.92
[210]
137.34
[247]
9.01
208.98
10.81
79.90
112.41
40.08
[251]
12.01
140.12
132.91
35.45
52.00
58.93
63.55
[247]
162.50
[252]
167.26
151.96
[257]
19.00
[223]
157.25
69.72
72.61
196.97
178.49
4.00
164.93
1.01
114.82
126.90
192.22
55.85
83.80
138.91
[260]
207.20
6.94
174.97
24.31
54.94
[258]
Mercury
Molybdenum
Neodymium
Neon
Neptunium
Nickel
Niobium
Nitrogen
Nobelium
Osmium
Oxygen
Palladium
Phosphorus
Platinum
Plutonium
Polonium
Potassium
Praseodymium
Promethium
Protactinium
Radium
Radon
Rhenium
Rhodium
Rubidium
Ruthenium
Samarium
Scandium
Selenium
Silicon
Silver
Sodium
Strontium
Sulfur
Tantalum
Technetium
Tellurium
Terbium
Thallium
Thorium
Thulium
Tin
Titanium
Tungsten
Uranium
Vanadium
Xenon
Ytterbium
Yttrium
Zinc
Zirconium
Symbol
Hg
Mo
Nd
Ne
Np
Ni
Nb
N
No
Os
O
Pd
P
Pt
Pu
Po
K
Pr
Pm
Pa
Ra
Rn
Re
Rh
Rb
Ru
Sm
Sc
Se
Si
Ag
Na
Sr
S
Ta
Tc
Te
Tb
Tl
Th
Tm
Sn
Ti
W
U
V
Xe
Yb
Y
Zn
Zr
Atomic
number
80
42
60
10
93
28
41
7
102
76
8
46
15
78
94
84
19
59
61
91
88
86
75
45
37
44
62
21
34
14
47
11
38
16
73
43
52
65
81
90
69
50
22
74
92
23
54
70
39
30
40
A value given in brackets denotes the mass of the longest-lived or best-known isotope,
Page 10 of 11
Atomic
mass
200.59
95.94
144.24
20.18
[237]
58.69
92.91
14.01
[259]
190.20
16.00
106.42
30.97
195.08
[244]
[210]
39.10
140.91
[145]
231.04
226.03
[222]
186.21
102.91
85.47
101.07
150.36
44.96
78.96
28.09
107.87
22.99
87.62
32.07
180.95
[98]
127.60
158.93
204.37
232.04
168.93
118.71
47.88
183.85
238.03
50.94
131.29
173.04
88.91
65.39
91.22*
School of Chemistry, UNIVERSITY OF KWAZULU-NATAL PIETERMARITZBURG
SUBJECT, COURSE & CODE: CHEM099 and CHEM199 :FOUNDATION CHEMISTRY
NOVEMBER 2009 EXAMINATION
Electro-negativity values for selected elements
(in order of Atomic Number)
Element
Electro-negativity value
H
2.1
He
0
Li
0.98
Be
1.57
B
2.04
C
2.55
N
3.04
O
3.44
F
3.98
Ne
0
Na
0.93
Mg
1.31
Al
1.61
Si
1.9
P
2.19
S
2.58
Cl
3.16
Ar
0
K
0.82
Ca
1
Br
2.96
Page 11 of 11