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A) NAMIBIA UNIVERSITY OF SCIENCE AND TECHNOLOGY

FACULTY OF HEALTH AND APPLIED SCIENCES

DEPARTMENT OF NATURAL AND APPLIED SCIENCES

QUALIFICATION: BACHELOR OF SCIENCE

QUALIFICATION CODE: 07BOSC LEVEL: 5

COURSE CODE: GNC501S COURSE NAME: GENERAL CHEMISTRY 1A

SESSION: JUNE 2019 PAPER: THEORY |

DURATION: 3 HOURS MARKS: 100

FIRST OPPORTUNITY EXAMINATION QUESTION PAPER

EXAMINER(S) DR. EUODIA HESS

MoperRATOR: | DR. MARIUS MUTORWA

INSTRUCTIONS

Answer ALL the questions.

Write clearly and neatly.

Number the answers clearly

All written work must be done in blue or black ink and sketches can

be done in pencil

5. No books, notes and other additional aids are allowed

Pepe

PERMISSABLE MATERIALS

Non-programmable calculators

ATTACHMENTS

1. List of useful constants

2. Periodic Table

THIS QUESTION PAPER CONSISTS OF 8 PAGES (Including this front page, list of useful constants

and Periodic Table)

SECTION A: MULTIPLE CHOICE QUESTIONS >

os

There are 20 multiple choice questions in this section. Each question carries 3 marks.

Answer ALL questions by selecting the letter of the correct answer.

Choose the best possible answer for each question, even if you think there is another

possible answer that is not given.

What type of ions have names ending with —ide?

A. Only cations

B. Only anions

C. Only metal ions

D. Only gaseous ions

When Group 2A elements form ions, they

A. B.

G

Dz.

Lose two protons

Lose two electrons

Gain two protons

Gain two electrons

What is the correct name for N27 ion?

A.

B.

G.

D.

Nitrate ion

Nitride ion

Nitrogen ion

Nitrite ion

Aluminium is a Group 3A metal. Which ion does Al typically form?

A.

B.

C.

D.

Noe AI8t

Als- Al5+

Bohr’s atomic model ....

A. proposes that electrons occupy specific energy levels.

B. explains the emission spectra of hydrogen atoms.

C. predicts the energy level of multi-electron atoms

D. bothAandB

orbitals are spherically symmetrical.

A. f B. d Gc p

D. s

The n= 1 shell contains p sub-orbitals. All other shells contain p sub-orbitals.

A. 3,6

B. 0,3

C. 6,2 D. 0,6

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[60]

8. There are orbitals in the second shell.

A. 1

908

BRWHN

9. Anunknown amount of C3Hs was burned completely to H2O and CO, with 36 g of H20 recovered.

How many moles of the hydrocarbon were originally present?

A. 0.25

B. 0.50

G. 2 36

D. -

10. Acompound having an empirical formula of SO3 is found to have a molecular weight of 80. What is

its molecular formula?

A. S309

B. S206

C. SO3

D. SOq

11. Balance the following reaction:

S$ +02 SO3

A. S+ O3 ~ SO3

B. 4S +202 —- 4SO3

C. 284302 —- 2S03

D. 38+202 —- 3S03

12. What is the formula weight of Al2(SOq)3?

A. 150

B. 123

C. 342

D. 315

13. Standard conditions (STP) are:

0°C and 2 atm

32°F and 76 torr

273 K and 760 mmHg

4°C and 7.6 mmHg GO >

14. What is the name of the following hydrocarbon according to the IUPAC rules?

3,3-dimethyl-5-propylhexane

6,6-dimethyl-4-propyloctane

3,3-diethyl-5-propyloctane

3,3-dimethyl-5-propyloctane OO P>

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15. Which of the following alkanes would have the highest boiling point?

GN@>

(a) (v) ec (CH

CH3- CH2- CH2- CH2- CH2- CH)- CH3 CH3- - CH

CH, CH3

(c) (d) CH3~CH3- CHp- CH~ cu- CH3 CH3- (a CH2- a CH3

CH3 CH; CH3

(a) (b) (c) (d)

16. Which of these would be least soluble in water?

A.

B.

C.

D.

octanol (CH3CH2CH2CH2CH2CH 2CH2CH2-OH)

butanol (CH3CH2CH2CH2-OH)

pentanol (CH3CH2CH2CH2CH2-Oh)

hexanol (CH3CH2CH2CH2CH2CH2-OH)

17. The alcohol shown below is a:

9NOR>

(CH3)2CHOH

Primary alcohol

Secondary alcohol

Tertiary alcohol

Allylic alcohol

18. A hydrocarbon with the general formula C,H2n-2 can be:

A. B.

C.

D.

an alkyne or a cycloalkene

an alkyne ora cyclolkane

a cycloalkane or an alkene

a cycloalkene

19. Smoke is an example of a colloid termed:

A. B.

C.

D

a foam

an aerosol

a gel

. sol

20. What is the boiling point in °C of a solution of a 2.15 m aqueous solution of glycerol? (Kp =

0.512°C/m)? A.

B

C.

D

101.1

100.2

100

1.1

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SECTION B: [40]

There are FIVE questions in this section. Answer all Questions.

Show clearly, where necessary, how you arrive at the answer as the working will carry marks to.

Question 1 [11]

a) Food we eat are degraded in our bodies to provide energy for growth and function. A

general overall equation for this complex process represents the degradation of glucose

to carbon dioxide and water:

C6H120¢ + O2 > CO2 + H20

If 856 g of glucose is consumed by a person over a certain period, what is the mass of

carbon dioxide produced? (5)

b) Urea is prepared by reacting ammonia with carbon dioxide:

NH3 (g) + CO2 (g) (NH2)2CO (aq) + H20 (I)

In one process 637.2 g of NH3 is treated with 1142 g of COz.

(i) Which of the two reactants is the limiting reagent? (3)

(ii) Calculate the mass of (NH2)2CO formed. (1)

(iii) How much excess reagent (in grams) is left at the end of the reaction? (2)

Question 2 [6]

(a) How many grams of potassium dichromate are required to prepare a 250 mL solution

whose concentration is 2.16 M? (3)

(b) Describe how you would prepare 5.00 x 10? mL of a 1.75 M sulphuric acid solution, starting

with a 8.16 M stock solution. (3)

Question 3 [9]

a) Sulfur hexafluoride is a colorless and odourless gas. Due to its lack of chemical reactivity, it is

used as an insulator in electronic equipment. Calculate the pressure (in atm) exerted by 1.82

moles of gas in a steel vessel of volume 5.43 Lat 69.5 °C. (2)

b) Calculate the volume (in L) occupied by 7.40 g of ammonia at STP. (2)

c) A flammable gas made up of carbon and hydrogen is found to effuse through a porous barrier

in 1.50 min. Under the same conditions and pressure it takes an equal volume of bromine

vapour 4.73 min to effuse through the same barrier. Calculate the molar mass of the unknown

gas. (5)

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Question 4

A solution contains 750 g of ethanol (CH3CH20H) and 85.0 g of sucrose (molar mass = 180 g/mol).

The volume of the solution is 810.0 mL. Determine:

(a) the density of the solution.

(b) the mass percent of sucrose in the solution.

(c) the mole fraction of sucrose.

(d) the molality of the solution.

(e) the molarity of the solution.

Question 5

a) Write the IUPAC names of the following compounds:

(i)

~~

(b) State the functional group in each of the following compounds:

|

(ii) CH; Cc ——OH

CH; C ——OCH, (iii)

END OF EXAMINATION

[9]

(1) (2) (2) (2) (2)

[5]

(2)

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USEFUL CONSTANTS:

Gas constant, R = 8.3145 J: mol: K= 0.083145 dm?: bar - molt: K= 0.08206 L atm mol: K?

1 Pa‘m?=1kPa.L =1N-m =1)J

1 atm = 101 325 Pa = 760 mmHg = 760 torr

Avogadro’s Number, Na = 6.022 x 1073 mol

Planck’s constant, h = 6.626 x 1074 Js

Speed of light, c = 2.998 x 108 ms

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