JAMB CBT Chemistry Questions and Answers 2027/2028: Latest UTME Updates

Effective JAMB Chemistry Answers.

From my experience, preparing for JAMB Chemistry means more than just memorising answers. Candidates make good use of the Chemistry syllabus. It is important to also practise calculations, recognise question patterns and become comfortable with computer based test (CBT).

This guide gives JAMB Chemistry practice questions and answers covering the parts of the JAMB Chemistry syllabus. The questions are practice items for revision. They are not leaked JAMB questions. Are not presented as questions from any JAMB examination.

The official JAMB Integrated Brochure and Syllabus System (IBASS) gives the Chemistry syllabus. Is the starting point, for deciding what candidates should study. The stated objectives include understanding chemical principles, interpreting data relating chemistry to other sciences and applying chemistry to industry and everyday life.

JAMB Chemistry Syllabus: What Candidates Should Study

The official Chemistry syllabus covers broad areas including:

Separation of mixtures and purification of chemical substances

Chemical combination and stoichiometry

Kinetic theory of matter and gas laws

Atomic structure and periodicity

Chemical bonding

Oxidation-reduction reactions

Acids, bases and salts

Solubility

Water and its treatment

Air and environmental chemistry

Energy changes in chemical reactions

Reaction rates

Chemical equilibrium

Electrochemistry and electrolysis

Metals and their compounds

Non-metals and their compounds

Organic chemistry

Chemistry of petroleum

Macromolecules and polymers

Chemistry and industry.

The official IBASS Chemistry document should be checked periodically because it is the authoritative syllabus source for JAMB preparation. JAMB’s main website also directs candidates to IBASS for syllabus and programme information.

JAMB Chemistry Questions and Answers

Topic 1: Separation of Mixtures and Purification

Question 1

Which method is most suitable for separating a mixture of sand and sodium chloride?

A. Sublimation

B. Dissolution, filtration and evaporation

C. Fractional distillation

D. Chromatography

Answer: B — Dissolution, filtration and evaporation

Explanation: Sodium chloride dissolves in water while sand does not. The sand can therefore be removed by filtration, while evaporation of the filtrate recovers the salt.

Topic tested: Separation of mixtures.

Question 2

Which method is most appropriate for separating ethanol from water?

A. Filtration

B. Sublimation

C. Fractional distillation

D. Decantation

Answer: C — Fractional distillation

Explanation: Ethanol and water are miscible liquids with different boiling points. Fractional distillation is suitable for separating miscible liquids whose boiling points are relatively close.

Topic tested: Distillation.

Question 3

A substance that changes directly from solid to vapour on heating undergoes

A. condensation

B. sublimation

C. freezing

D. evaporation

Answer: B — Sublimation

Explanation: Sublimation is the direct conversion of a solid to a gas without passing through the liquid state.

Topic tested: Physical changes and separation techniques.

Topic 2: Atomic Structure and Periodicity

Question 4

An atom has 17 protons and 18 electrons. What is its charge?

A. +1

B. −1

C. +17

D. −17

Answer: B — −1

Explanation: The atom has one more electron than proton. Since electrons carry negative charge, the net charge is −1.

Topic tested: Atomic structure and ions.

Question 5

What is the maximum number of electrons that can occupy the first shell of an atom?

A. 2

B. 4

C. 8

D. 18

Answer: A — 2

Explanation: The first principal energy level can accommodate a maximum of two electrons.

Topic tested: Electronic configuration.

Question 6

Which of the following elements belongs to Group 18?

A. Chlorine

B. Sodium

C. Argon

D. Calcium

Answer: C — Argon

Explanation: Argon is a noble gas and belongs to Group 18 of the periodic table.

Topic tested: Periodic classification.

Question 7

Across a period of the periodic table, atomic radius generally

A. increases

B. decreases

C. remains constant

D. first disappears and then increases

Answer: B — decreases

Explanation: Nuclear charge increases across a period while electrons are added to the same principal energy level. The stronger attraction generally decreases atomic radius.

Topic tested: Periodic trends.

Topic 3: Chemical Bonding

Question 8

The bond formed when sodium transfers an electron to chlorine is

A. metallic

B. covalent

C. ionic

D. coordinate

Answer: C — Ionic

Explanation: Sodium loses an electron to form Na⁺ while chlorine gains an electron to form Cl⁻. The electrostatic attraction between the ions produces an ionic bond.

Topic tested: Ionic bonding.

Question 9

Which substance contains covalent bonds?

A. NaCl

B. MgO

C. H₂O

D. KBr

Answer: C — H₂O

Explanation: The hydrogen and oxygen atoms in water share electrons, forming covalent bonds.

Topic tested: Covalent bonding.

Question 10

A coordinate bond is formed when

A. each atom contributes one electron

B. one atom supplies both bonding electrons

C. electrons are completely transferred

D. protons are shared between atoms

Answer: B — One atom supplies both bonding electrons

Explanation: In a coordinate or dative covalent bond, both electrons in the shared pair originate from one atom.

Topic tested: Chemical bonding.

Topic 4: Mole Concept and Stoichiometry

Question 11

How many moles are present in 18 g of water?

[H = 1, O = 16]

A. 0.5 mol

B. 1.0 mol

C. 2.0 mol

D. 18 mol

Answer: B — 1.0 mol

Explanation: Relative molecular mass of H₂O = 2(1) + 16 = 18. Therefore:

18 g ÷ 18 g mol⁻¹ = 1 mol.

Topic tested: Mole concept.

Question 12

What is the molar mass of CaCO₃?

[Ca = 40, C = 12, O = 16]

A. 68 g mol⁻¹

B. 84 g mol⁻¹

C. 100 g mol⁻¹

D. 112 g mol⁻¹

Answer: C — 100 g mol⁻¹

Explanation: 40 + 12 + 3(16) = 100 g mol⁻¹.

Topic tested: Relative molecular mass.

Question 13

How many molecules are present in one mole of a substance?

A. 6.02 × 10²¹

B.6.02 × 10²²

C.6.02 × 10²³

D.6.02 × 10²⁴

Answer: C — 6.02 × 10²³

Explanation: One mole contains Avogadro’s constant, approximately 6.02 × 10²³ particles.

Topic tested: Mole concept and Avogadro’s constant.

Question 14

What mass of NaOH is contained in 0.5 mol of NaOH?

[Na = 23, O = 16, H = 1]

A. 10 g

B. 20 g

C. 40 g

D. 80 g

Answer: B — 20 g

Explanation: Molar mass of NaOH = 23 + 16 + 1 = 40 g mol⁻¹.

Mass = 0.5 × 40 = 20 g.

Topic tested: Stoichiometric calculations.

Question 15

In the equation

2H₂ + O₂ → 2H₂O,

how many moles of water are produced when 2 moles of H₂ react completely with sufficient oxygen?

A. 1 mol

B. 2 mol

C. 3 mol

D. 4 mol

Answer: B — 2 mol

Explanation: The balanced equation shows a 2:2 mole ratio between H₂ and H₂O.

Topic tested: Chemical equations and stoichiometry.

Topic 5: Gas Laws

Question 16

According to Boyle’s law, at constant temperature, the pressure of a fixed mass of gas is

A. directly proportional to its volume

B. inversely proportional to its volume

C. equal to its temperature

D. independent of volume

Answer: B — Inversely proportional to its volume

Explanation: Boyle’s law states that P ∝ 1/V at constant temperature.

Topic tested: Gas laws.

Question 17

A gas occupies 2 dm³ at a pressure of 100 kPa. If the volume is reduced to 1 dm³ at constant temperature, what is its new pressure?

A. 50 kPa

B. 100 kPa

C. 200 kPa

D. 400 kPa

Answer: C — 200 kPa

Explanation:

P₁V₁ = P₂V₂

100 × 2 = P₂ × 1

P₂ = 200 kPa.

Topic tested: Boyle’s law.

Question 18

Which gas law states that the volume of a fixed mass of gas is directly proportional to its absolute temperature at constant pressure?

A. Boyle’s law

B. Charles’ law

C. Dalton’s law

D. Graham’s law

Answer: B — Charles’ law

Explanation: Charles’ law relates gas volume to absolute temperature at constant pressure.

Topic tested: Gas laws.

Topic 6: Acids, Bases and Salts

Question 19

Which of the following is a strong acid?

A. CH₃COOH

B. HCl

C. H₂CO₃

D. H₂S

Answer: B — HCl

Explanation: Hydrochloric acid is a strong acid that ionises extensively in aqueous solution.

Topic tested: Acids and bases.

Question 20

A solution with pH 2 is

A. strongly acidic

B. weakly acidic

C. neutral

D. alkaline

Answer: A — Strongly acidic

Explanation: A pH substantially below 7 indicates an acidic solution; pH 2 represents a strongly acidic solution.

Topic tested: pH and acidity.

Question 21

Which compound is a salt?

A. HCl

B. NaOH

C. NaCl

D. NH₃

Answer: C — NaCl

Explanation: Sodium chloride is an ionic salt formed from sodium and chloride ions.

Topic tested: Salts.

Question 22

The reaction between an acid and a base to form salt and water is called

A. oxidation

B. neutralisation

C. polymerisation

D. hydrolysis

Answer: B — Neutralisation

Explanation: Acid-base neutralisation produces salt and water when an acid reacts with a suitable base.

Topic tested: Acid-base reactions.

Topic 7: Solubility and Solutions

Question 23

A solution that contains the maximum amount of solute that can dissolve at a specified temperature is

A. dilute

B. unsaturated

C. saturated

D. concentrated gas

Answer: C — Saturated

Explanation: A saturated solution contains the maximum amount of dissolved solute possible under the stated conditions.

Topic tested: Solubility.

Question 24

Which factor generally increases the solubility of most solid solutes in water?

A. Decreasing temperature

B. Increasing temperature

C. Removing the solvent

D. Freezing the solution

Answer: B — Increasing temperature

Explanation: The solubility of many solid substances increases as temperature rises, although this is not universal for every solute.

Topic tested: Solubility.

SEE ALSO : JAMB Questions and Answers for all Subjects

Topic 8: Oxidation and Reduction

Question 25

Oxidation can be defined as

A. gain of electrons

B. loss of electrons

C. gain of neutrons

D. loss of protons only

Answer: B — Loss of electrons

Explanation: Oxidation involves loss of electrons. Reduction involves gain of electrons.

Topic tested: Redox reactions.

Question 26

In the reaction

Zn + Cu²⁺ → Zn²⁺ + Cu,

which substance is oxidised?

A. Zn

B. Cu²⁺

C. Cu

D. Zn²⁺

Answer: A — Zn

Explanation: Zinc changes from Zn to Zn²⁺ by losing electrons. Loss of electrons is oxidation.

Topic tested: Oxidation-reduction reactions.

Question 27

The reducing agent in the reaction

Zn + Cu²⁺ → Zn²⁺ + Cu

is

A. Zn

B. Cu²⁺

C. Cu

D. Zn²⁺

Answer: A — Zn

Explanation: Zinc donates electrons to Cu²⁺. A substance that donates electrons is the reducing agent.

Topic tested: Redox chemistry.

Topic 9: Electrolysis

Question 28

During electrolysis, positively charged ions move towards the

A. anode

B. cathode

C. electrolyte surface only

D. salt bridge

Answer: B — Cathode

Explanation: Positive ions, or cations, are attracted to the negatively charged cathode in an electrolytic cell.

Topic tested: Electrolysis.

Question 29

The electrode at which oxidation occurs is the

A. cathode

B. anode

C. electrolyte

D. salt bridge

Answer: B — Anode

Explanation: Oxidation occurs at the anode. A useful memory aid is OIL: Oxidation Is Loss of electrons.

Topic tested: Electrochemistry.

Topic 10: Rates of Chemical Reactions

Question 30

Which of the following generally increases the rate of reaction between a solid and an acid?

A. Decreasing surface area

B. Increasing surface area

C. Removing the acid

D. Lowering reactant concentration

Answer: B — Increasing surface area

Explanation: A powdered solid exposes more surface to the reacting acid, increasing the frequency of effective collisions.

Topic tested: Reaction rates.

Question 31

A catalyst increases the rate of a reaction by

A. increasing the amount of product permanently

B. lowering the activation energy

C. increasing the mass of reactants

D. changing the chemical formula of the products