SCHOOL OF CHEMISTRY & PHYSICS
UNIVERSITY OF KWAZULU-NATAL, WESTVILLE CAMPUS
CHEM199 : FOUNDATION CHEMISTRY
NOVEMBER 2013 EXAMINATION
DURATION: 3 HOURS
TOTAL MARKS: 100
External Examiner:
Internal Examiners:
Dr Matthew Ackerman
Dr Roshila Moodley (W) (Course Coordinator)
Mr Muvhango Rasalanavho (PMB) (Course
Coordinator)
Ms Pravena Bhujrajh (PMB)
Dr Chantal Koorbanally (W)
Dr Sheila Tewari (W)
Instructions:
•
This paper consists of 19 pages which include a Periodic Table of elements,
Table of Relative atomic masses and Table of Electronegativities.
•
Please check that you have them all.
•
Each question is marked out of 20 marks.
•
Marks for individual sub-questions are given in brackets after each question.
•
Answer all four questions in the answer booklet provided.
Students are requested, in their own interests to write legibly
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
QUESTION 1 [20 MARKS]
1.1.
The indigo dye used to colour blue jeans has the formula C16H10N2O2. How
many moles of indigo are there in 50.0 g of the dye?
(Mm of C16H10N2O2 = 262.28 g mol-1)
1.2.
1.3.
A.
0.962 moles
B.
262 moles
C.
0.191 moles
D.
131 moles
Which of the following contains the smallest percentage by mass of sulfur?
A.
H2 S
B.
SO3
C.
SO2
D.
H2S2O7
A compound with empirical formula CH2O is found to have a molar mass of
180 g mol−1. The molecular formula of the compound is:
A.
C5H10O5
B.
C2H4O2
C.
C3H6O3
D.
C6H12O6
Page 2 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
1.4.
1.5.
1.6.
1.7.
Avogadro’s number represents the number of atoms in:
A.
28.02 g of nitrogen
B.
65.39 g of zinc
C.
32.00 g of oxygen
D.
24.19 g of fluorine
Which of the following formulas represent an empirical formula?
A.
C9H9N3O2
B.
C12H16N2O12
C.
C8H12O4
D.
C16H32O2
Theoretical yield refers to:
A.
The quantity obtained in practice
B.
The expected yield
C.
The experimental yield
D.
The yield obtained at STP
Which of the following determines the amount of product in a reaction:
A.
The excess reagent
B.
The limiting reagent
C.
The percentage yield
D.
The amount of starting material added
Page 3 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
1.8.
For the reaction:
3H2(g) + N2(g) → 2NH3(g)
How many moles of ammonia (NH3) will be produced if 3 moles N2 reacts with
6 moles H2.
1.9.
A.
3
B.
6
C.
2
D.
4
What volume does one mole of gas occupy at room temperature (1 atm and
25 ͦC)?
A.
22.40 dm3
B.
2.240 dm3
C.
24.45 dm3
D.
25.55 dm3
1.10. The total number of sublevels and orbitals in a shell or energy level 6 are
____ and _____ respectively.
A.
6 and 36
B.
36 and 6
C.
36 and 72
D.
6 and 72
Page 4 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
1.11. Which of the following may represent an excited-state electron configuration
for a cobalt atom (27Co)?
A.
[Ar]4s13d6
B.
[Ar]4s23d7
C.
[Ar]4s13d8
D.
[Ar]4s23d6
1.12. In Bohr’s atomic theory, when an electron moves from one energy level to
another level which is further from the nucleus, the following would have
happened:
A.
Energy is emitted.
B.
Energy is absorbed.
C.
No change in energy occurs.
D.
Light is emitted.
1.13. Using IUPAC rules, give the name for Pb(NO3)2.
A.
Lead(III) nitride
B.
Lead(II) nitrite
C.
Lead(II) nitrate
D.
Lead(III) nitrate
Page 5 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
1.14. In which pair do both compounds exhibit predominantly ionic bonding?
A.
Na2SO3 and BH3
B.
KI and O3
C.
NaF and H2O
D.
RbCl and CaO
1.15. Which of the following is the Lewis dot structure for the bromide ion?
A.
B.
C.
D.
1.16. When preparing a standard solution of potassium hydrogen phthalate in a
volumetric flask
A.
It is acceptable to suck up some liquid from the top of the flask if you
have passed the graduation mark
B.
You are allowed to use the solution if you have passed the graduation
mark, as long as you have passed it by a few drops only
C.
You would need to prepare another solution if you have passed the
graduation mark, even if by a small amount
D.
The bottom of the meniscus needs to be as close to the graduation
mark as possible
Page 6 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
1.17. The process of repeatedly heating, cooling and weighing a sample until two
successive mass readings agree is known as:
A.
Heating to constant mass
B.
Drying
C.
Concordancy
D.
Drying and firing
1.18. When heating a hydrated salt in a crucible to determine its empirical formula,
the crucible lid should…
A.
Be on to prevent moisture from rehydrating the salt
B.
Be off to allow the water molecules to escape
C.
Partially cover the crucible
D.
Be on to allow the sample to heat up
1.19. When filtering under suction you should pour the mixture in the following way
whilst applying suction
A.
Directly onto the centre of the filter paper to avoid loss of sample
B.
Along the sides of the Buchner funnel
C.
Onto the filter paper from a beaker so that the spout can help direct
the mixture onto the filter paper
D.
Onto the centre of the filter paper by pouring it down a glass rod
Page 7 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
1.20. When separating pure Alum from crude Alum, the percentage recovery may
be high because
A.
The temperature during boiling could have been too high resulting in
spattering
B.
Some crystals could have been lost due to carelessness
C.
Some Alum could have remained dissolved in the water due to
insufficient boiling resulting in loss during filtration
D.
The final drying of the sample could have been incomplete
[20]
QUESTION 2 [20 MARKS]
2.1.
Eucalyptus leaves contain oil which is poisonous to many animals besides the
Koala bears. The chief constituent in eucalyptus oil is a substance called
eucalyptol, which contains 77.87% carbon, 11.76% hydrogen, and the
remainder oxygen.
a) Determine the empirical formula for eucalyptol.
(5)
b) A mass spectrum of eucalyptol shows a peak at about 154 amu. What is
the molar mass of eucalyptol?
(1)
Page 8 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
2.2.
The molecular formula of allicin, the compound responsible for the
characteristic smell of garlic, is C6H10OS2. (Mm of C6H10OS2 = 162.3 g mol-1)
a) Determine the mass percentage composition of carbon in allicin.
(2)
b) Calculate the mass of carbon in a 12.83 g sample of allicin.
(2)
c) How many atoms of sulfur are present in 5.87 g of allicin?
(4½)
2.3.
Dilute solutions of potassium permanganate, KMnO4, can be used to treat
ulcers and mild fungal infections of the hands or feet.
a) What mass of potassium permanganate would a chemist need to prepare
500.0 mL of a 0.4283 M KMnO4 solution?
(3½)
b) What volume (mL) of a 0.1597 M dilute potassium permanganate solution
can be made from 25.00 mL of the chemist’s solution, mentioned in a)
above?
(3)
[20]
Page 9 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
QUESTION 3 [20 MARKS]
3.1
Spillage of sulfuric acid (H2SO4) is hazardous to the environment. A technician
spills 45.0 kg of pure sulfuric acid on the storeroom floor. As a current
Science Foundation student with a clear understanding of the mole concept,
you are called on for help.
There are two proposals from two Science Foundation teams:
i. Team A proposed that they add a solution of 6.00 M NaOH to the spilled
acid, which reacts as follows:
2NaOH(aq) + H2SO4(aq)
Na2SO4(aq) + 2H2O(l)
ii. Team B proposed that they sprinkle powdered calcium carbonate (CaCO3)
over the spilled acid, which reacts as follows:
CaCO3(s) + H2SO4(aq)
CaSO4(s) + H2O(l) + CO2(g)
a) Determine the volume of NaOH that is required to neutralize the acid.
(4)
b) Determine the mass (g) of CaCO3 that is required to neutralize the acid.
(2)
c) Explain which one of the two reagents is more sensible to use to deal with
the acid spillage.
(2)
Page 10 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
3.2
As we move towards ‘greener’, more environmentally friendly practices, the
aim is to provide more fuel efficient cars which leave a lesser carbon footprint
or find alternative sources of fuel. A typical reaction for the combustion of
octane (C8H18, a component in gasoline/petrol) in a car is as follows:
2C8H18(l) +
25O2(g)
16CO2(g)
+
18H2O(g)
a) If 255.0 g of octane and 1510.0 g of oxygen are present, determine the
mass (g) of CO2 that will be released from this car into the atmosphere?
(6)
b) What mass (g) of the excess reagent remains unreacted?
(3)
3
c) In a carbon emissions test, it was found that 50.2 dm of CO2 was actually
released into the atmosphere at room temperature (1 atm, 25⁰C). What is
the percentage yield of this reaction?
(3)
[20]
Page 11 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
QUESTION 4 [20 MARKS]
4.1
Radon has 39 isotopes, with mass numbers ranging from 193 to 231. Of
these, the most stable isotope is
222
Rn.
a) Work out the number of each type of subatomic particles found in
222
Rn.
(2)
b) Apart from the notation for this isotope given above, write down two other
notations that can be used to represent it.
(1)
4.2
Using an element in Period 5 and Group 2 answer the following questions:
a) Identify this element by writing its name and symbol.
(1)
b) Write the expanded ground state electronic configuration for this element.
(1)
c) Write down its Lewis dot notation and the abbreviated spectroscopic
electron configuration.
(1)
d) State the number of electron(s) found in the fourth energy level of this
element.
(1)
4.3
State the following:
a) Hund’s rule of maximum multiplicity
(1)
b) Pauli’s exclusion principle
(1)
Page 12 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
4.4
A table of eight electronic configurations, A to F, is given below.
NOTE:
These electronic configurations can be used more than once in
answering questions a) to d).
Write the appropriate letter(s) (A to F) for each answer.
Some questions have more than one answer and some may have no
answer. Each question a) to d) is worth one mark.
A.
1s22s1
B.
C.
[Ne]
D.
E.
1s22s22P5
F.
2, 5
[Ar]4s23d2
From the entries in the above table which:
a) have only two unpaired electrons
b) have a helium electron core
c) represent/s a non-metal
d) can be represented as
12X
(5)
Page 13 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
4.5
Study the following statements and correct them where necessary:
a) Sodium bicarbonate has the formula NaCO3
(1)
b) Iron(III) sulfite has the formula FeSO3
(1)
4.6
Give the charge on the ion which is underlined:
a) Ag3PO4
b) NbO2
(1)
4.7
Give the systematic name of each of the following compounds:
a) P4S10
b) Cl2O5
(1)
4.8
Explain what is meant by the phrase/term:
a) Oxidizing agent
b) Oxidation
(2)
[20]
Page 14 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
QUESTION 5 [20 MARKS]
5.1
A technician performed titrations with a standard 0.1054 M NaOH solution to
standardise three acid solutions.
For each titration, 25.00 mL of the acid
solution was pipetted into a conical flask and titrated with the standard
solution. The average titre volumes for the concordant results of three
titrations are presented in the table below. An indicator was used to detect
the end-point of the reaction in the flask.
Table 1: Titration of 25.00 mL of acid with 0.1054 M NaOH solution
Acid name
Acid formula
Average
titre
(mL)
Hydrochloric acid
HCl
10.46
Citric acid
(CH2)2COH(COOH)3
15.60
Unknown acid
Adipic acid
(CH2)4(COOH)2
Succinic acid
(CH2)2(COOH)2
25.64
a) Explain what is meant by each of the following terms.
i.
Standard solution
ii.
Concordant results
iii.
End-point
(3)
b) Name one acid from the above table that is:
i.
Monoprotic
ii.
Diprotic
iii.
Triprotic
(3)
Page 15 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
c) For the titration between NaOH and HCl:
i.
Write a balanced equation for the reaction (include state symbols).
(2)
ii.
Name an indicator that can be used for the reaction.
(1)
iii.
Calculate the number of moles of the NaOH solution.
(1)
iv.
Determine the concentration of the HCl solution.
(3)
d) The technician has to decide if the unknown acid is adipic acid
(146.14 g mol-1) or succinic acid (118.09 g mol-1). The acid solution was
prepared in a 250.0 mL volumetric flask using 1.980 g of the unknown
salt.
i.
Write a balanced equation for the reaction between adipic acid and
the base (include state symbols).
(2)
ii.
Determine the identity of the unknown acid.
(5)
[20]
Page 16 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
Page 17 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
Page 18 of 19
University of KwaZulu-Natal, School of Chemistry and Physics, Pietermaritzburg Campus
November 2013 Main Examination Session, CHEM199 Foundation Chemistry
Page 19 of 19