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545/1
CHEMISTRY
Paper 1
July/Aug. 2024
𝑿
𝟔𝟑
WAKISHA JOINT MOCK EXAMINATIONS
Uganda certificate of lower secondary education
MOCK EXAMINATIONS – JULY / AUGUST 2024
CHEMISTRY
Paper 1
2 hours
INSTRUCTIONS TO CANDIDATES.
This paper consists of two sections A and B.
It has a total of six examination items.
Section A has two compulsory items.
Section B has two parts, I and II. Answer one item from each part.
Answer four items in all.
SECTION A
Answer all the items in this section.
Item 1

SCORING GUIDE FOR ITEM 1

Category + Dangers / side effects Evaluation Total

Function/use
(a) + (b): C + F = T2 = 06 (c) Di + De + Dm = D3 = 06 Sb + Df = E2 = 06
C = T1 = 04 De + Dm = D3 = 06
Sb = E1 = 03
F = 00 Di + Dm = D3 = 06
Di + De = D3 = 04 Df = E1 = 03
De= D2 = 04
Di = D1 = 01

T = 06 max D = 06 max E = 06 max 18

C = category Di = Danger identified Sb = similarity
F = Function/use De = Danger explained Df = Difference
Dm = Danger mitigated
An argument took place between a brother and his sister concerning how to wash clothes

clean. The brother said white star or magic give best results, but the sister insists on blue

star or OMO. They failed to reach an argument.

Task.

Using the knowledge of chemistry,

(a) Classify the products. (one category)

C
Or soap detergent

Accept: soapless detergents

(b) Briefly explain how one of the two products work.

F
Soap acts by lowering the surface tension between dirt and water. This is because soap

molecules are made up of two parts; water- soluble (hydrophilic) and dirt-soluble

part(hydrophobic). The hydrophobic part of soap penetrates/ dissolves the dirt while the

hydrophilic part of the soap dissolves in water. With constant agitation/rinsing, dirt is

removed from the fabric/cloth and carried away by the water.

C + F = T2 = 06

(c) State the dangers of using the product you refer to in (b) excessively.
Di De
Soap cannot work well with hard water, hence wasted. This is prevented by using
Dm
detergents.

Or

Water with soap or detergent, if poured in water bodies, form layers which prevent
entry of oxygen and sunlight, which may kill aquatic life. This is prevented by treating
such water before disposal into the lake.
Or
 Some detergents are corrosive, burn fingers during washing. This can be prevented by

using soap, washing machine, glove wearing.

Di + De + Dm = D3 = 06

(d) Give the similarity and difference between the cleaning agents used by the brother.

(one difference, one similarity)

Similarities
Sm
Both are cleaning agents

Or

Both have polar (hydrophilic) ends and non-polar (hydrophobic) ends.

Differences
Df
Soap forms scum with hard water, while detergents do not form scum.

Or

Soap contains carboxyl group, while detergents contain sulphonates or sulphates.

Sm + Df = E2 = 06 Total = 18

Item 2

SCORING GUIDE FOR ITEM 2 Total

Category + Reason +example Properties and use Dangers to the

(Only category and reason are scored) environment

Cr + Ci= C2 = 04 3-4P + 1U = X3 = 05 Mi + Mm = I2 = 03
Cr = C2 = 04 3-4P = X2 = 03 Mi + Mm = I2 = 03
Ci = C1 = 03 1-2P + 1U = X2 = 03 Mi + Mm = I2 = 03
1-2P = X1 = 02
1U = X1 = 02

C = 04 max X = 05 max I = 03 max 12

A farmer in a village without electricity always keeps his garden tools outside the house

after the work. After some time, his tools developed brown coating and he was disturbed

what happened?

Task.

As a chemistry student,

(a) point out the environmental factors that led his tools develop the brown coating.
Ci Cr
Presence of air/oxygen which reacts with iron

Or

Presence of water/moisture to dissolve atoms of iron.

Cr + Ci= C2 = 04

(b) State the properties of one of the environmental factors listed in (a) above.

Air/ oxygen
P P P P
Forms oxides with other elements, colorless, no smell, mixture of gases.

Moisture / water

solvent for ionic compounds, colorless, no smell, neutral.

(c) What are the uses of the environmental factor in (a) above?

Oxygen

Supports combustion, respiration/ breathing, welding operations, fuel in rockets.

Moisture / water

Domestic use, component of plant/animal bodies, cooling agent in industries, hydrolysis of

salts. 3-4P + 1U = X2 = 05

(d) What is the impact of the brown coating on the tools and how is this solved?
Mi Mm
Make tools weak and blunt, reducing their work rate. Can be mitigated by oiling, greasing,

painting, stainless steel, galvanization, storing in a cool, dry place.

 OR

Make tools less attractive, can be mitigated by oiling, greasing.

Mi + Mm = I2 = 03 Total = 12
SECTION B

PART I
(Attempt one item from this part)
SCORING GUIDE FOR ITEMS 3 AND 4
Process of production with raw Dangers Social benefits Total
materials
Cp = {3Rm+V+Pp+Pc+Pr+Cd+Ch} Di+De+Dm=S3=06 Sb + Se +Si=B3=06
= P3 = 06 Di +Dm=S3=06 Sb+ Si=B3=06
1Rm+Any one of (V, Pp, Pc, Pr, Cd)
De+Dm=S3=06 Se+Si=B3=06
= P2 = 05
Di+De=S2=04 Se =B2=06
1Rm + (V, Pp, Pc, Pr, Cd) = P1 = 04
De =S2=04 Sb =B2=06

Di =S2=04 Si=00

Dm=00
P = 06 max S = 06 max B = 06 max 18
Rm = Raw materials Di = Danger identified Sb = social benefit
V = vessel De = Danger Se = effect of the
Pp = physical process explained social benefit
Pc = chemical process Dm = Danger Si = impact of the
Cd = conversion to the desired mitigated social benefit
product
Ch = coherence
Cp = complete process
Item 3
A certain rice scheme has been growing rice for a long period of time. However, the yield
has greatly reduced. After analysis, the manager found out that the soils had become
nitrogen deficient and would require nitrogen-based fertilizers. The manager has been
informed that the fertilizer can be made industrially from nitrogen
Task

As a chemistry student, make a write-up to the manager on how the fertilizer can be made.

The raw materials are nitrogen, hydrogen, sulphuric acid, finely divided iron catalyst,

platinum, air etc

Rm Rm
Nitrogen from fractional distillation of liquid air and hydrogen gas from natural gas are first

purified.

The purified nitrogen and hydrogen gases are mixed in a 1:3 ratio. This gas mixture is

compressed to about 150–250 atmospheres (atm) pressure using multi-stage compressors.

The compressed gas mixture is passed over a finely divided iron catalyst, often promoted
Rm
with small amounts of aluminium oxide. The reaction occurs in a reactor at high

temperature (400–500°C) and high pressure (150–250 atm and ammonia is produced by

Haber process.

𝑁2 (𝑔) + 3𝐻2 (𝑔) 2𝑁𝐻3 (𝑔)

The reaction mixture is cooled to -33°C, this liquefies ammonia which is then purified by

methanation process.

Ammonia produced is heated in air (oxygen), in the presence of platinum catalysts forming

nitrogen monoxide and water in the tank.

Rm Rm
4𝑁𝐻3 (𝑔) + 𝑂2 (𝑔) 4𝑁𝑂(𝑔) + 6𝐻2 𝑂(𝑙)

Nitrogen monoxide produced is further oxidized to nitrogen dioxide by heating.

𝑁𝑂(𝑔) + 𝑂2 (𝑔) 2𝑁𝑂2 (𝑔)

Nitrogen dioxide produced is dissolved in water in the presence oxygen in a tank forming
Rm
nitric acid.

Rm
 4𝑁𝑂2 (𝑔) + 𝑂2 (𝑔) + 2𝐻2 𝑂(𝑙 ) 4𝐻𝑁𝑂3 (𝑎𝑞)

Nitric acid is heated with ammonia in a tank at 1000C – 1800C to form ammonium nitrate

𝐻𝑁𝑂3 (𝑎𝑞) + 𝑁𝐻3 (𝑔) 𝑁𝐻4 𝑁𝑂3 (𝑎𝑞)

The fertilizer is further concentrated and converted to solid form.

Cp ={3Rm+ V + Pp + Pc + Pr + Cd + Ch} = P3 = 06

At least 3 three At least 3 three

Side effects and mitigation

• Poisonous fumes by waste gases which when inhaled can cause respiratory disorders.

This can be mitigated by fitting catalytic converters in exhaust pipes of the machines to

convert oxides of nitrogen into nitrogen.

• Air pollution from waste gases and fumes, particularly acidic ones like nitrogen dioxide,

can lead to acid rain, which harms buildings, bridges, and agricultural productivity. It

can be mitigated by encouraging the use of renewable energy instead of fossil fuels,

installing scrubbers in exhaust systems to neutralize acidic gases, and using catalytic

converters to convert nitrogen oxides into nitrogen.

• Land pollution from oil spills and plastic waste decreases soil fertility and contaminates

water sources, threatening ecosystems and food security. This can be mitigated by

enforcing environmental laws and promoting recycling and waste reduction.

• Deforestation for construction increases atmospheric carbon dioxide, contributing to

global warming and food scarcity. This can be mitigated by planting fast-growing trees.

Additionally, emissions of greenhouse gases alter rainfall patterns, and transitioning to

renewable energy is essential to address these climate issues.

Social benefits

• Employment opportunities; increased income among residents hence improved

standards of living.

• Source of revenue to the government, through taxes, improved infrastructure, for

example health facilities, roads, hence community development.

• Development of infrastructure e.g roads which facilitate trade improved income thus

better standards of living

• Development of infrastructure e.g access to better and cheaper medical services

and thus better and health community

• Development of infrastructure e.g schools, access to better and cheaper education

and thus better and a well-informed community.

Sb + Se + Si = B3 = 06 Total = 18

Item 4.

Kilembe Mine on the foothills of Rwenzori Mountain is estimated by government

geologists to contain tones of the ore that contain copper. The production of copper has

halted due to low copper prices and political instability. However, the demand for copper

has since increased. The Ministry of Energy and Mineral Development has cleared an

investor to restore the mining of copper with minimum environmental impact. The youth

in the area are wondering how the extraction process will be done. The head teacher has

appointed you to explain to the youth how the process will be done and how they can benefit

from each task. Prepare a presentation that you will use during the sensitization.

Responses
The process involves concentration of the ore by froth flotation, roasting in air, and

purification by electrolysis.
Rm
The ore of copper, usually copper pyrites, is crushed into a powder and added to water with

a frothing agent (oil) in a concentration tank. Then agitated by blowing air, the copper ore

gets trapped into the oil on the surface. It is skimmed off and dried. An acid is added to

break the froth, and the ore is dried. The dried ore is roasted in air to obtain Copper(I)

sulphide, Iron (II) oxide, and sulphur dioxide.

Rm Rm
2𝑪𝒖𝑭𝒆𝑺𝟐 (𝑠) + 4𝑶𝟐 (𝑔) 𝐶𝑢2 𝑆(𝑠) + 2𝐹𝑒𝑂(𝑠) + 3𝑆𝑂2 (𝑔)
Rm
Then, the mixture is heated with Silicon (IV) oxide to remove Iron (II) oxide impurity as Iron

(II) silicate/molten slag.

Rm
𝐹𝑒𝑂(𝑠) + 𝑆𝑖𝑂2 (𝑔) 𝐹𝑒𝑆𝑖𝑂3 (𝑙)

The slag is separated out, and Copper(I) sulphide is heated in a limited supply of air to form

blister copper/impure copper.

𝐶𝑢2 𝑆(𝑠) + 𝑂2 (𝑔) 2𝐶𝑢(𝑠) + 𝑆𝑂2 (𝑔)

The blister (impure) copper is purified by electrolysis, making it the anode; a pure copper

strip is used as the cathode, and the electrolyte is copper (II) sulphate solution in an

electrolytic tank.

Accept/Allow: Well-labeled diagram for electrolysis of copper (II) sulphate solution.

The anode dissolves in the electrolyte, dropping the impurities, while copper (II) ions

migrate to the cathode, gain electrons, and are discharged as pure copper.

𝐶𝑢 2+ (𝑎𝑞) + 2𝑒 𝐶𝑢(𝑠)
The pure copper is then drawn into wires to conduct electricity.

Cp ={3Rm+ V + Pp + Pc + Pr + Cd + Ch} = P3 = 06

At least 3 three At least 3 three

Side Effects

• Air pollution by sulphur dioxide, which forms acid rain that destroys iron roofings

and houses, crumbles rocks, and lowers pH of soil or water, affecting aquatic

life/micro-organisms.

Or

𝑆𝑂2 (𝑔) + 𝐻2 𝑂(𝑙 ) 𝐻2 𝑆𝑂3 (𝑎𝑞)

Mitigation: Insert catalytic converters in the exhaust fume pipes.

• Sound pollution from machines, which can cause deafness/hearing loss. Mitigation:

Installation of sound absorbers in the factory.

• Water pollution from industrial waste (effluent). Mitigation: Proper disposal of

wastes and treatment of industrial wastes.

Di + De + Dm = S3 = 06

Social Benefits

• Creates job opportunities (employment) for citizens who will earn income/money to

improve standards of living.

Or

• Government collects revenue from taxes based on copper production.

Sb + Se + SiPart
= B3 II.
= 06 Total = 18
 (Attempt one item from this part)

SCORING GUIDE FOR ITEM 5 AND 6

Category + Reason + Impact of human activity Benefit of the natural Total

example and composition on the natural resource resource

(Example is not scored)

Ci+R+3Co = N2=06 Mi+ Me + Mm = M3=04 Bi + Eb=Be2 = 05

Ci+R+1Co = N2=06 Mi + Mm = M3=04 Bi = Be1 = 05

Ci+R+1Co = N2=05 Me + Mm = M3=04 Eb = Be1= 03

Ci+R= N2=00 Mi + Me = M2=02

R = 00
Mi + = M1=01

Me = M1=01

N = 06 max M = 04 max Be = 05 max 15

Ci = category identified Mi = impact of human Bi = Benefit identified

R = Reason activity identified Eb = Benefit explained

Co = components Me = explanation

Mm = mitigation

Item 5.

Recently, there has been a rapid climate change for the past years leading to increased

temperature changes of the earth and the extinction of some species of organisms.

Government through the National Environment Management Authority is planning to

organize Environmental awareness workshop on the effect of climatic change. You have

been invited at one of the local FM radio to talk about the issue.

Task

As a chemistry student who has studied about climate change, prepare your presentation

for the talk show.

Responses (There are many natural resources, water, air, forests/trees, rocks)

Climate change is due to destruction of natural resources like water, vegetation, cover,

forests etc.

Trees/forests, vegetation and water are renewable natural resources since they can easily

be replenished/replaced within a short time

Forests contain trees which are made of carbon, hydrogen and oxygen

Water is made of hydrogen and oxygen,

Air contains oxygen, rare gases, carbon dioxide, nitrogen etc

Ci + R + 3Co = N2 = 06

Impacts of activities on natural resources; how it occurs and mitigates

• Crop/ animal husbandry; trees and other vegetation are cut down to create space;
Mi Me
water cycle is disrupted hence less rain is received. This can be mitigated by planting

trees that grow and mature fast.

• Destruction of vegetation for installing machines, roads, buildings, leads to

accumulation of carbon dioxide in the atmosphere which absorbs heat from the sun,

hence global warming. This can be mitigated by planting trees that mature faster.

• Increase in population releases toxic wastes and other wastes like plastics which are

thrown into landfills. These emit gases like carbon dioxide, methane mainly during
 burning and decomposition, which are greenhouse gases, accumulate in the

atmosphere, hence global temperature increases. This can be mitigated by setting up

waste disposal plants with catalytic converters, planting faster-growing trees.

• Crop/ animal husbandry; trees and other vegetation are cut down to create space;

carbon dioxide accumulates in the atmosphere and traps heat from the sun hence

global temperature rises and rainfall formation reduces. This can be mitigated by

planting trees that grow and mature fast.

• Mills emit greenhouse gasses as result of burning carbon/ fossil fuels. They trap heat

from the sun which results into temperature rise. This can be mitigated by use of

alternative fuel sources, wind and solar power or planting trees that grow and mature

so fast.

• Mills rises toxic wastes and other wastes like plastics which are thrown into landfills.

These reduce soil productivity hence some crops will dry out. The waste may also be

washed to different water sources and this makes the water unsafe. It can be mitigated

by putting strict laws against disposal of wastes.

• Swamp reclamation involves removal of water by adding rocks, clay soil which disrupts

the water cycle hence reduced rainfall. It also leads to reduced water quality This can

be mitigated by putting strict laws on swamp reclamation/ educating people on the

importance of swamps

Mi + Me + Mm = M3 = 04

Benefits/importance of natural resources to everyday life (mentioned benefits and

explained)
Bi
• Forests/ trees provides us with oxygen; during photosynthesis oxygen is released and

can be used during respiration Eb

• Forests/ trees reduce greenhouse effects; since the use carbon dioxide during

photosynthesis and oxygen which can be used during respiration is released

• Trees from the forest are used as fuels; since they burn to release heat energy which

can be used for cooking etc.

• Air facilitates photosynthesis process where carbon dioxide from air together with

water in presence of sunlight trapped by chlorophyll form glucose and oxygen.

• Air is used for respiration where food is broken down in the body to produce energy

for the proper functioning of body systems.

• Water is a key resource in various industrial processes. It is used for manufacturing,

cooling machinery, cleaning products, and as a solvent in chemical processes.

• Habitat for many aquatic organisms; water bodies like lakes, dams, pools contain

necessary conditions for survival of aquatic animals

Bi + Be = Be2 = 05 Total = 15

Item 6.

Some people living in the Rock area are poor because crops cannot grow well. They have

decided to relocate to another area, but the area member of parliament (MP) has organized

the sensitization workshop to the other ways they would make use of the Rocks.

Task.

As a chemistry student, you have been selected to advise the people of the area. Make a

write-up you will present to the people of the area.

Rocks are non-renewable natural resources because they cannot be easily replenished once

used up.

Rocks contain limestone, mica, quartz, feldspar, and minerals such as zinc, iron, copper, etc.

Ci + R + Mi
3Co = N2 = 06 Me
• Dust from the quarry pollutes air and causes breathing problems. Mitigation: Sprinkle

water in the quarry to suppress dust/wear PPEs, e.g., masks

• Explosions damage buildings Mitigation: Ban human settlement near the quarry.

• Explosions cause sound pollution and affect people with heart ailments. Mitigation:

Sirens are sounded to alert people to take safety/relocate.

Mi + Me + Mm = M3 = 04

Benefits:
Bi
• Rocks contribute to soil formation through weathering. Eb

Or

• Rocks are used for tourist attraction, which brings revenue to the government.

• Some rocks are preserved due to their appearance and used to decorate buildings.

• Some rocks, due to their strength, are used in tarmacking roads/making pavements.

• Some rocks are preserved for historical importance, worship, performing cultural

rites, etc.

• Caves act as hiding places/homes for animals/biodiversity conservation.

• Some rocks are used as scrubbing stones for the feet since they are hard and rough.

ASSESSMENT
Bi + Be = Be2 =GRID
05 Total = 15

ITEM 1
Basis Code T D E TOTAL

Score 06 06 06 18

ITEM 2

Basis Code C X I TOTAL

Score 04 05 03 12

ITEM 3 and 4

Basis Code P S B TOTAL

Score 06 06 06 18

ITEM 5 and 6

Basis Code N M Be TOTAL

Score 06 04 05 15