S3 Chemistry National Exam | NESA 2025

Section A: Attempt ALL questions (55 marks)

1) Circle the correct answer in each of the following questions:

i) Which of the following carriers fits better with someone who graduated in chemistry?

A) Economist.

B) Pharmacist.

C) Financial analyst.

D) Market research analyst.

Answers

The corrected answer is B

ii) Chemistry is applied in the following processes EXCEPT:

A) Water treatment.

B) Making school desks.

C) Manufacture of paints.

D) Making soaps and detergents.

Answers

The correct answer is: B

iii) What is the risk associated with the misuse of chemistry knowledge?

A) Advanced agricultural productivity and food security.

B) Improved environmental protection and human health.

C) Increased development of new technologies with no harmful effects.

D) Accidental chemical reactions causing harm to individuals or communities.

Answers

The corrected answer is D

2) Circle the correct answer for each of the following questions:

i) Which of the following statements is true about covalent bonds? 

A) They are stronger than ionic bonds.

B) They result in the formation of charged particles.

C) They involve the sharing of electrons between two non-metal atoms.

D) They form between two metals by transferring electrons.

Answers:

The correct answer is: C
ii) What does the term "malleability" refer to for metals?

A) The ability of metals to conduct electricity.

B) The ability of metals to resist corrosion.

C) The ability of metals to be drawn into thin wires.

D) The ability of metals to be hammered into thin sheets.

Answer

The correct answer is D

iii) Which of the following substances contains metallic bonds?

A) C (Graphite)

B) Fe (Iron)

C) NaCl

D) CO₂

Answers:

The correct answer is B

 

3. Fill in the blank spaces with the provided underlined terms. Each term will be used once: biodegradable wastes, non-biodegradable wastes, waste materials.

i) The ………………….………….…... are substances discarded after their intended use, often resulting from manufacturing, consumption, or daily activities.

Answers

i) Waste materials

ii) When discarded, the………………….………….…..., such as plastics and metals, persist in the environment for long periods.

Answers

ii) Non-biodegradable wastes

 

iii) The ………………….………….…..., like food scraps and paper, can naturally decompose by natural processes.

iii) Biodegradable wastes

4) State whether each of the following statements about oxygen is true (T) or false (F).

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i) Oxygen gas turns into blue the moist red litmus paper False
ii) Oxygen is colorless, odorless, and tasteless in its gaseous form True
iii) The equation below shows one method of preparation of oxygen:

 

False

5) Match each term in the left column with its corresponding definition in the right column of the table.

S/N	Term		S/N	Definition
i.	Unsaturated solution		A)	Is a solution that contains the maximum amount of solute at an elevated temperature.
ii.	Supersaturated solution		B)	Is a solution that contains less solute than that it can dissolve at a given temperature.
iii.	Saturated solution		C)	is a solution that contains as much solute as can dissolve in the given solvent at a given temperature.

 

Answers:

i-------- > B
ii ------- >A
iii ------ >C

 

6. Circle the correct answer for each of the following questions:

i) Which of the following formulae of oxides is wrong?

A) K₂O

B) SO₂

C) P₂O₃

D) Ca₂O

Answers:

The correct answer is D

ii) Which of the following oxides is amphoteric?

A) Al₂O₃

B) Na₂O

C) MgO

D) SO₂

Answers

 The correct answer is A
iii) Non-metal elements react with oxygen to give oxides which are;

A) neutral

B) basic

C) acidic

D) amphoteric

Answers:

The correct answer is C

 

7. Match each compound in the left column with its corresponding boiling point in the right column of the table.

S/N	Compound		SN	Boiling point in Kelvin (K)
i)	Pentane		A)	231
ii)	Ethane		B)	90
iii)	Propane		C)	184
iv)	Methane		D)	309

 

Answers:

i (Pentane)------ > D (309 K)
ii (Ethane) ------ >B (90 K)
iii (Propane)------> C (184 K)
iv (Methane)----- > A (231 K)

 

8. Circle the correct answer in each of the following questions:

i) Why is it that in a laboratory, most of the apparatus and reaction vessels are made of transparent glass or plastic material?

A) To ensure the durability of the equipments.

B) To prevent contamination of solutions.

C) To allow easy observation of reactions and contents.

D) To reduce the cost of production of equipments.

Answers:

The correct answer is C
ii) The following safety symbol is used on a bottle containing a chemical substance Y. Why is the symbol used on this bottle?

Answers

The correct answer is B) flammable and can easily catch fire and burn.

iii) iii) Why is it that in a laboratory, it is recommended to use a new spatula each time you take chemicals from a different container?

A) To ensure that the spatula stays clean for future use.

B) To prevent that one spatula can be broken as it is used many times.

C) To reduce the risk of spills and accidents.

D) To avoid cross-contamination and maintain the purity of each chemical.

Answers:

The correct answer is D

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iv) Why is it that apparatus V is more preferable than apparatus B for preparing solutions in a laboratory?

Answers

The correct answer is B

9. State whether each of the following statements about the properties of elements in the Periodic Table is true (T) or false (F).

i) i) Both sodium (Na) and sulphur (S) are in the same period 3. Na is a good conductor of electricity while sulphur is a bad conductor. True (T)
ii) Carbon in the form of graphite is a bad conductor of electricity. False (F)

iii) Both magnesium (Mg) and chlorine (Cl) are in the same period 3. The melting point of Mg is lower than that of Cl. False (F)
iv) Zinc metal reacts with dilute sulphuric acid to give zinc sulphate solution and hydrogen gas.

(Atomic numbers: Na=11, Mg=12, S=16, Cl=17)

True (T)

10. Circle the correct answer in each of the following questions:

i) Why is nitrogen (N₂) considered as inert and less reactive?

A) Nitrogen is a noble gas diatomic molecule.

B) Nitrogen molecules have a low molecular weight.

C) Nitrogen molecules are held together by a strong triple bond.

D) Nitrogen molecules contain hard non-polar covalent bonds.

Answers

The correct answer is C
ii) The correct product formed when ammonia (NH3) reacts with sulphuric acid (H2SO4) is:

A) NH4_SO₄

B) NH₄(SO₄)₃

C) (NH₄)₃SO₄

D) (NH₄)₂SO₄

Answers

 The correct answer is D

iii) Nitrogen reacts with magnesium to form magnesium nitride according to the following equation.

A) 3Mg(s) + N₂(g)------ > Mg₃N₂(s)

B) Mg₃ (s) + N₂ (g)------ >  Mg₃N₂(s)

C) 3Mg(s) + N₂(g)------ > 3 MgN(s)

 D) 3Mg(s) + 2 N(g)----- >  3 Mg₃N₂(s)

Answer

The correct answer is A

iv) Which of the following is one way to prevent eutrophication?

A) Using chemical fertilizers excessively.

B) Advise farmers to avoid cultivating near river banks.

C) Increasing industrial wastewater discharge.

D) Reducing the use of organic farming practices.

Answers:

The correct answer is B

11. Fill in the blanks of the following equations, with the appropriate compound.

i) Na2O(s) + H₂O(l)------------ --- > …………..

Answers

Na2O + H2O → 2NaOH

ii) Mg(s) + H2SO4(aq)------------- > MgSO4(aq) + ................

Answers

H₂ (hydrogen gas)

iii) NaCl(s) + H₂SO₄(l)-------------- > NaHSO₄(aq) + ................

Answers

HCl

iv) CaCO₃(s) + 2HCl(aq) ----------- > ........... + CO₂(g) + H₂O(l)

Answers

CaCl₂

12. Show the correct answer for each of the following questions:

i) The correct chemical formula for the compound formed between potassium ions (K+) and phosphate ions (PO43-) is:

A) K₃PO₄

B) 3KPO₄

C) K(PO₄)₃

D) K3(PO₄)₂

Answers:

 

The correct answer is A (K₃PO₄)

ii) A correctly balanced symbolic equation for the following word equation, Sodium + Chlorine----------> Sodium chloride is:

A) 2Na(s) + 1/2Cl₂(g) 2NaCl(s)

B) Na(s) + 1/2Cl₂(g) 2NaCl(s)

C) 2Na(s) + Cl₂(g) 2NaCl(s)

D) 1/2Na(s) + Cl₂(g) NaCl(s)

(Atomic numbers: Na = 11, Cl = 17)

Answers

The correct answer is C

iii) What is the correctly balanced symbolic equation for the following word equation Lithium + Oxygen--------- > Lithium oxide?

A) Li(s) + O₂(g) Li₂O(s)

B) Li(s) + 1/2O₂(g) Li₂O(s)

C) 2Li(s) + O₂(g) Li₂O(s)

D) 4Li(s) + O₂(g) 2Li₂O(s)

(Atomic numbers: Li = 3, O = 8)

Answers

The correct answer is D

iv) Which set of stoichiometric coefficients x, y and z, is correct for the equation, xKClO3(s) yKCl(s) + zO2(g) ?

A) x = 3, y = 3, z = 3

B) x = 2, y = 2, z = 3

C) x = 1, y = 2, z = 3

D) x = 2, y = 1, z = 3

Answers

The correct answer is B

13. Glucose is a simple sugar and good energy source for living organisms, with molecular formula, C₆H₁₂O₆ and molecular mass of 180 g/mol. Given the atomic masses: H =1, C = 12, O =16.

i) What is the percentage by mass of carbon element in glucose?

A) 36%

B) 40%

C) 44%

D) 50%

Answers

The correct answer is Carbon % = (72/180) ×100 = 40% → B

ii) What is the percentage by mass of oxygen element in glucose?

A) 63.33%

B) 46.12%

C) 40.6%

D) 53.33%

Answers:

The correct answer is Oxygen % = (96/180) ×100 = 53.33%----> D

iii) What is the percentage by mass of hydrogen element in glucose?

A) 3.33%

B) 4.17%

C) 6.66%

D) 1.33%

Answers

The correct answer is Hydrogen % = (12/180) ×100 = 6.66% --->C

iv) How many moles are there in 9.0 grams of glucose?

A) 0.05 moles B

B) 1,620 moles

C) 0.5 moles

D) 171 grams

Answers:

The correct answer is Moles = 9/180 = 0.05--->A

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14. Find out the correct answer for each of the following questions:

i) Which one of the following pieces of apparatus is NOT used during titration process?

A) Burette

B) Test tube

C) Pipette

D) Conical flask

Answers

The correct answer is B (Test tube)

ii) ii) The picture below shows the part of burette. It indicates three readings of three eyes, A, B and C of three observers during titration process. Which of the three eyes indicates the accurate reading of the burette?

Answers:

The correct answer is C (Eye B)

iii) A 20.00 cm³ of sodium hydroxide was neutralized with exactly 25.00 cm³ of 0.04 mol/l hydrochloric acid. How much is the molarity of sodium hydroxide?

A) 0.04 mol/l

B) 0.2 mol/l

C) 0.5 mol/l

D) 0.05 mol/l

Answers

The correct answer is 0.05 mol/L → D

iv) Given that the concentration of a hydrochloric acid solution is 0.24 mol/l, what is this concentration in grams per liter? Given that the molar mass of hydrochloric acid is 36.5 g/mol.

A) 8.76 g/l

B) 36.74 g/l

C) 8.52 g/l

D) 0.0066 g/l

Answers

The correct answer is 0.24 × 36.5 = 8.76 g/L → A 

15. The general formula for carboxylic acids is CnH2n+1COOH.

i) Write the structural formula for a carboxylic acid with:

a) two-carbon atoms.

b) three-carbon atoms.

Answers

a) CH₃COOH
b) CH₃CH₂COOH

ii) Write an equation of the reaction between a two-carbon atoms carboxylic and sodium metal. 

Answers

2CH₃COOH + 2Na → 2CH₃COONa + H₂

iii) Determine the molecular mass for the three-carbon atoms carboxylic acid.

(Atomic masses: H = 1, C=12, O =16)

Answers

C₃H₆O₂ → (3×12 + 6×1 + 2×16) = 74 g/mol

Section B: Attempt any three (3) questions (30 marks)

16. The figure below shows the setup of laboratory preparation of hydrogen chloride. Observe it and answer the associated questions.

i) The correct name for the apparatus X is:

A) Dropping funnel

B) Distillation column

C) Glass tube

D) Dropper

Answers

The correct answer is A (Dropping funnel)
ii) What is the correct name for the apparatuses Y?

A) Conical flasks

B) Pipettes

C) Burettes

D) Delivery tubes

Answers

The correct answer is D (Delivery tubes)
iii) The role of conc. sulphuric acid (Z), in the washing bottle is:

A) to neutralize the basic gas.

B) to dissolve the gas being prepared.

C) to dry the gas being prepared.

D) to absorb the gas being prepared.

Answers

The correct answer is C (to dry gas)

iv) Select the three (3) correct physical properties for hydrogen chloride, from the following list. Correct properties:

a) HCl boils at -850C. It has a higher boiling point than water.

b) HCl a highly polar substance. It is very soluble in water.

c) HCl is solid at room temperature.

d) HCl melts at -1140C. It has a lower melting point than water.

e) HCl has a density of 1.19 g/cm3. It is denser than air.

Answers
The correct answers are b, d, e

v) Complete the following table with the missing information for reactions (A), (B), (C) and (D), where two reagents were added on HCl.

Answers:

Reaction	Main product	Observation
(A)	AgCl	White precipitate
(B)	—	White precipitate forms
(C)	NH₄Cl	White fumes
(D)	—	White fumes

 

17. Provide answers for each of the following questions:

i) Identify two (2) correct properties for oxygen.

A) Oxygen constitutes the inactive part of air.

B) Oxygen has no effect on litmus papers. It is a neutral gas.

C) The density of oxygen is 1.43g/cm3. It is denser than air.

D) Oxygen exists as a triatomic molecule (O3). (Density of air = 1.225 g/cm3)

Answers:

The correct choices are B and C

ii) The following figure shows three different methods of collecting gases.

a) What is the suitable method for collecting oxygen?

The correct answer is Over water method
b) Which one is “upward delivery (downward displacement of air)”?

The answer is light gases
c) Which one is “downward delivery (upward displacement of air)”?

The answer is heavy gases

d) Which method is suitable for gases which are insoluble in water or slightly soluble in water and that do not react with water?

Answer is Over water

iii) Observe the chart of reactions starting with magnesium (Mg) and sulphur (S) and answer the related questions.

Give the chemical formulae for compounds X, Y, Z and W.

X = MgO
Y = Mg(OH)₂
Z = SO₂
W = H₂SO₃

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18. This question concerns alkenes and alcohols.

i) The general formula for alcohols is:

A) CnH3nOH

B) C2nH5nOH

C) CnH2n+1OH

D) CnH3n+1OH

Answer: C

ii) State whether each of the following statements is true (T) or false (F).
a) The boiling point of ethanol is higher than the that of ethene.  True (T)
b) Both pent-1-ene and pent-2-ene are chain isomers.  False (F)
c) Alcohols do not conductor electricity. True (T)
d) Alkenes are used in manufacture of plastics during polymerizations reactions. True (T)

iii) The chart below shows the reactions that occur with propanol. Observe the chart and answer the related question.

a) Write the IUPAC name for CH3-CH2-CH2OH. 

Propan-1-ol

b) Give the main products H and I.
H → Sodium propoxide + H₂
I → Propene

c) Suggest the reagent and condition J and K.
J → Concentrated H₂SO₄, 170°C
K → Oxidation (e.g. KMnO₄ or K₂Cr₂O₇)

19. Water pollution refers to the contamination of water bodies.

i) i) Fill in the blank spaces with the provided underlined terms. Each term will be used once: non-point source, sewage, point source.

a) The easily identified source of water pollution such as municipal discharge pipe is called Point source

b) Generally Sewage consists of faeces, urine and laundry waste.
c) A pollution source for which the source cannot be easily identified is known as Non-point source

ii) Match each danger of polluted water in the left column with its corresponding example of causal agent in the right column of the table.

S/N	Danger of polluted water		SN	Causal agent
)      A)	Eutrophication		1)	Carbon dioxide (CO2)
B)	Health Hazards		2)	Phosphates (PO43-)
C)	Acidification of water bodies		3)	Bacteria

A ----- > 2
B ----- > 3
C------ > 1

iii) Match each water pollutant in the left column with its corresponding example of pollutant in the right column of the table.

SN	Water pollutant		SN	Example
A)	Pathogens		1)	Mercury
B)	Plastic		2)	Escherichia coli
C)	Chemical waste (Industrial waste)		3)	Water hyacinth
D)	Alien species		4)	Polythene

Answers

A------ > 2
B------ > 4
C------ > 1
D------ > 3

 

20. In an experiment, the dilute hydrochloric acid (HCl) was reacted with limestone (CaCO3) and a gas was released according to the data in the table.

Time (min)	0.0	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0	4.5	5.0	5.5	6.0
Volume (cm3)	0	8	15	21	26	30	33	36	38	39	40	40	40

 

i) At what time did the reaction stop?

Reaction stops at 5.0 minutes

ii) Which gas is released in the above reaction?

The answer is O₂

iii) Write a balanced chemical equation for the above reaction.
CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O

iv) Explain how each of the following factors affect the rate of reaction.
a) Powdered limestone at 40°C.

Answer: Catalyst → increases rate
b) Powdered limestone at 25°C.

Answer: Higher concentration → more collisions → faster reaction

v) Which reactant below will react the fastest with hydrochloric acid?

A) Powdered limestone at 40°C.

B) Powdered limestone at 25°C.

C) Limestone chips at 25°C.

D) Limestone chips at 40°C.

Justify your answer

A (Powdered limestone at 40°C)
Because greater surface area + higher temperature = fastest rate

 

Section C: Attempt any one (1) question (15 marks)

21. The solubility curves for different substances are shown in the figure below.

i) Generally, the solubility of salts;

A) decreases with increase of temperature.

B) remains unchanged with decrease of temperature.

C) increases with increase of temperature.

D) decreases with decrease of temperature.

Answer:

C

ii) Which salt is more soluble at 200C?

A) KI

B) NaCl

C) KCl

D) KNO3

Answer

A (KI)

iii) What is the solubility of NaNO₃ at 100C?

A) 110g/100g of H₂O.

B) 30g/100g of H₂O.

C) 25g/100g of H₂O.

D) 80g/100g of H₂O.

Answers

D (80 g)

iv) At 300C, the solubility of KClO3 is:

A) 45g/100g of H₂O.

B) 30g/100g of H₂O.

C) 10g/100g of H₂O.

D) 50g/100g of H₂O.

Answers

C (10 g)

V) State whether each of the following statements is true (T) or false (F).
a) The solubility of KNO3 is higher than the solubility of NaCl, at 00C.  F
b) The solubility of NH3(g) decreases with increase of temperature.  T
c) At 700C, the solubility of NH4Cl is 60g/100g of H2O.  T
d) The solubility of KClO3 is 20g/100g of H2O, at 900C. F
e) At 00C, the solubility of KNO3 is lower than the solubility of NH4Cl while at 600C the solubility of KNO3 is higher than the solubility of NH4Cl.  T

 

vi) Describe a chemical test to distinguish between each of the pairs of the following ions. In each case, state the reagent, condition and expected observable change.

a) Fe2+(aq) and Fe3+(aq)

Fe²⁺ vs Fe³⁺

Reagent: NaOH

• Fe²⁺ → Green precipitate
• Fe³⁺ → Brown precipitate

 

b) SO₄₂-(aq) and SO₃₂(aq)

SO₄²⁻ vs SO₃²⁻

Reagent: BaCl₂ + dilute HCl

• SO₄²⁻ → White precipitate (insoluble in acid)
• SO₃²⁻ → White precipitate dissolves in acid

22. The flowchart below shows the industrial manufacture of sulphuric acid from sulphur as the starting raw material.

i) Name the process for industrial manufacture of sulphuric acid.

Contact process

ii) State any two (2) starting raw materials, required for manufacture of sulphuric acid.

Raw materials:
Sulphur
Oxygen (air)

iii) Write the reaction equation of oxidation of sulphur in air.

S + O₂ → SO₂

iv) Identify the:

a) gas G.

b) liquid M.

Answers:
a) Gas G = SO₃
b) Liquid M = H₂SO₄

v) Give the catalyst and temperature conditions for the formation of gas G.

Catalyst: V₂O₅
Temperature: ~450°C

 

vi) Write the reaction equation that occurs in absorption chamber.

SO₃ + H₂SO₄ → H₂S₂O₇ (oleum)

vii) Give any two uses of sulphuric acid.

Fertilizer production
Battery acid

viii) State any one environmental problem caused by this process of manufacture of sulphuric acid.

Acid rain

ix)  Propose one measure to minimize the environmental problem caused by this process of manufacture of sulphuric acid.

Use scrubbers to remove SO₂ emissions

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