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SCHOOL OF CHEMISTRY & PHYSICS

UNIVERSITY OF KWAZULU-NATAL, WESTVILLE CAMPUS
CHEM110 & CHEM195: GENERAL PRINCIPLES OF CHEMISTRY

JUNE 2015 MAIN EXAMINATION

Duration: 3 Hours
SECTION B
Internal Examiners: Dr N Nombona, Dr V Paideya, Mrs H Govender, Dr S Mahomed, Dr R Moodley,
Ms G Dawson
Moderators:

Student No. Seat Number:

INSTRUCTIONS:

1. Answer ALL questions.

2. Calculators may be used.
3. The pages of this paper must not be unpinned.
4. Your answers to section B must be written on the question paper in the spaces provided.
5. Use a ball point pen and write as clearly as possible.
6. This is Section B: Written Answer Questions, consisting of 10 Questions in 16 pages.
7. A periodic table and a data sheet are provided at the end of the Multiple Choice Questions
section.

SECTION SECTION A SECTION B

TOTAL
Questions 41 1 2 3 4 5 6 7 8 9 10
Maximum 50 1.5 5 4 3.5 3 4 11 11 4 3 100
Internal Mark
External Mark
IF A STUDENT IS FOUND GUILTY BY A STUDENT DISCIPLINE COURT OF CONTRAVENING THE ABOVE RULE –9(1)(e) – SHE/HE WILL SUFFER
ONE OR MORE OF THE FOLLOWING CONSEQUENCES:
Rule 9 (1)(e) WARNING: CANDIDATES WILL BE DISQUALIFIED IF:

(a) they introduce, or attempt to introduce, into any place where an examination is about to be conducted or is being conducted, any paper, book, note,
document or instrument, the use of which is not authorized by the examiner or the examination officer.
(b) they possess, use, or attempt to use during an examination, any paper, book, note, document or instrument the use of which is not authorized by
the examiner or the examination officer.
(c) they remove or attempt to remove from the examination room, any examination book or writing paper supplied by the University for the purposes
of answering an examination.
(d) they communicate or attempt to communicate any information relating to the examination to another candidate while the examination is in
progress.
(e) they use a false name or identity number in an examination.
(f) they commit any other fraudulent, deceitful or dishonest practice which would mislead or deceive the examiner or examination officer.
(i) Disqualification from entry to any examination.
(ii) Cancellation or forfeiture of examination results.
(iii) Deprivation of a degree, diploma or certificate obtained as a result of the offence.

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

SECTION B

QUESTION 1

A turquoise gem is a blue-green solid; it has a density of 2.65 g cm-3 and a mass of

2.5 g.

a) Which properties of the solid are extensive and intensive?

b) What is the volume of the turquoise gem?
[1.5]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

QUESTION 2

Many soft drinks contain sodium benzoate as a preservative. When you consume the
sodium benzoate, it reacts with the amino acid glycine in your body to form hippuric
acid, which is then excreted in the urine.

Hippuric acid has a molar mass of 179.17 g mol-1 and is 60.33% C, 5.06% H, and
7.82% N; the remainder is oxygen. What are the empirical and molecular formulas of
hippuric acid?

[5]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

QUESTION 3

Methanol, CH3OH, which can be used as a fuel in racing cars, can be made by the
reaction of carbon monoxide and hydrogen.

CO(g) + 2H2(g)  CH3OH(ℓ)

356 g of CO and 65.0 g of H2 are mixed and allowed to react.
a) What is the maximum mass of methanol that can be produced?
b) If the experimental mass of CH3OH produced is 250 g, what is the percentage
yield of methanol?
(Show all calculations)

[4]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

QUESTION 4

Balance the following redox equation in acidic medium using the half-reaction
method. (Show all relevant steps)

HS-(aq) + HSO3-(aq)  S2O32-(aq)

[3 ½]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

QUESTION 5

The following titration, done in triplicate, was carried out in the laboratory to determine if
an unknown acid was malonic acid (CH2(COOH)2, M=104.1 g mol-1). The acid solution
was prepared in a 250 mL volumetric flask using 1.99 g of the acid.

Acid(aq) + 2NaOH(aq) Sodium salt(aq) + 2H2O(ℓ)

Table 1: Titration of 20.00 mL acid solution against 0.09910 M NaOH solution

Titration 1 2 3
Final reading (mL) 32.03 31.64 32.10
Initial reading (mL) 1.15 1.02 1.31
Titre (mL)

a) Show, with the aid of calculations, if the acid is malonic acid (Only select the
titrations in closest agreement for the average titre value).
[3]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

QUESTION 6

A gaseous mixture made from 2.00 g of H2 (g) and 8.00 g of CO2 (g) is placed in a
10.0 dm3 vessel at 0°C ? What is the partial pressure of each gas, and what is the total
pressure in the vessel?
[4]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

QUESTION 7

a) Calculate the wave number of the photon of light associated with the electronic
transition between n = 7 and the ground state in the emission spectrum of H.
[3]

b) Scandium has an atomic number of 21.

(i) Using the periodic table, write the condensed electron configuration for
Sc. [1]

(ii) How many valence electrons does Sc have?

[½]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

c) List the angular momentum and the magnetic quantum numbers for the highest
energy electron (in bold) in vanadium, and state whether it is diamagnetic or
paramagnetic in character.
1s2 2s2 2p6 3s2 3p6 4s23d3
[1½]

d) Arrange the following atoms in order of increasing ionization energy:

Cl, Sb, Ne and Se. Provide an explanation for your answer.
[2]

e) Provide the balanced equation for the reaction of Li with nitrogen in the
atmosphere.

[1]

f) What is an oxoacid?
[1]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

g) Give an example of a neutral oxide

[1]

QUESTION 8

a) Draw the Lewis structure of MgBr2.

[1]

b) ClF3 does not obey the Octet Rule.

(i) Draw the Lewis structure of ClF3 and briefly discuss why it does not obey
the rule. [2]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

(ii) What is the molecular geometry and electron domain geometry around
the Cl atom?
[1]

c) Draw the Lewis structure for BF3, and give the electron domain geometry and
molecular geometry for B.
[2]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

d) Draw plausible Lewis structures for SO2. Using formal charge explain fully which
structure is most stable. Show all working.
[5]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

QUESTION 9

a) Both water and ammonia have a tetrahedral electron domain geometry yet the

bond angles in the molecules are different. Explain why this is the case using

diagrams in your answer.

[2]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

b) In the table shown, the boiling point is shown to increase from propane to

acetonitrile. Explain why this is the case.

[2]

Substance Molecular Mass Dipole Moment μ Boiling Point (K)

(u) (D)

Propane, CH3CH2CH3 44 0.1 231

Dimethyl Ether, CH3OCH3 46 1.3 248

Acetaldehyde, CH3CHO 44 2.7 294

Acetonitrile, CH3CN 41 3.9 355

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

QUESTION 10

Give the balanced chemical equations to show how you would make oleum.

[3]

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 University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, CHEM110 & CHEM195: General Principles of Chemistry

[TOTAL MARKS 50]

End of Section B

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