NECO Chemistry Questions and Answers 2026 [ESSAY & OBJ]
The National Examinations Council (NECO) Chemistry Examination is one of the core science subjects in the Senior School Certificate Examination (SSCE). It is compulsory for candidates seeking admission into courses such as Medicine, Pharmacy, Nursing, Engineering, Biochemistry, Microbiology, Agriculture, and other science-related programmes.
If you are preparing for the NECO Chemistry 2026 exam, this page provides likely NECO Chemistry Questions and Answers 2026 to help you prepare effectively before the examination.
The questions and answers contained in this guide are compiled based on the current NECO syllabus, previous examination trends, and frequently tested Chemistry topics. They are intended to serve as a comprehensive revision guide for candidates aiming to score excellent grades.
Whether you are targeting an A1 or simply want to improve your understanding of Chemistry, this guide will help you revise important concepts, formulas, calculations, and definitions before the examination.
This guide covers:
- NECO Chemistry Objective (OBJ) Questions and Answers
- NECO Chemistry Essay Questions and Answers
- Important Chemistry Topics to Revise
- Important Chemistry Formulas and Definitions
- Examination Instructions
- Tips to Score High in NECO Chemistry
NECO Chemistry Answers 2026
CHEMISTRY
01-10: CBADDBACEE
11-20: DDCDBCDAEB
21-30: BEEDADCEED
31-40: BBBCBBCDCE
41-50: DEEAAAEACC
51-60: ACCDEBCCDD
COMPLETED
(1ai)
(i) Dissolution of salt in water – Physical change
(ii) Burning of paper – Chemical change
(iii) Magnetization of iron – Physical change
(iv) Rusting of iron – Chemical change
(1aii)
Mercury is a liquid at room temperatur
(1bi)
I:
Calcium hydroxide, Ca(OH)₂
Ca = 40, O = 16, H = 1
Mr = 40 + 2(16 + 1)
= 40 + 34
= 74
II:
Lead(II) trioxonitrate(V), Pb(NO₃)₂
Pb = 207, N = 14, O = 16
Mr = 207 + 2(14 + 3×16)
= 207 + 2(62)
= 207 + 124
= 331
(1bii)
Isotopy is the existence of atoms of the same element having the same atomic number but different mass numbers.
(1biii)
(i) ₃E and ₁₉F
(ii) Lithium fluoride (LiF)
(1ci)
Charles’ law states that the volume of a fixed mass of gas is directly proportional to its absolute temperature, provided the pressure remains constant.
(1cii)
Given:
V₁ = 15 cm³
P₁ = 7.50 × 10⁴ N/m²
T₁ = 50°C = 323 K
At STP:
P₂ = 1.0 × 10⁵ N/m²
T₂ = 273 K
Using the combined gas law:
P₁V₁/T₁ = P₂V₂/T₂
V₂ = (P₁ × V₁ × T₂) / (P₂ × T₁)
V₂ = (7.50 × 10⁴ × 15 × 273) / (1.0 × 10⁵ × 323)
V₂ = 9.5cm³
∴ Volume of the gas at STP = 9.5 cm³
(1di)
(PICK ANY TWO)
(i) Diffusion
(ii) Brownian motion
(iii) Expansion of gases on heating
(iv) Gas pressure due to continuous molecular collisions
(v) Compression of gases
(vi) Effusion of gases through a tiny hole
(vii) Random (continuous) motion of gas molecules
(1dii)
Ionisation energy is the minimum amount of energy required to remove one electron from one mole of gaseous atoms to form one mole of gaseous positive ions.
(1diii)
Check the image below
(2ai)
(PICK ANY TWO)
(i) Haematite (Fe₂O₃)
(ii) Magnetite (Fe₃O₄)
(iii) Limonite (Fe₂O₃·3H₂O)
(iv) Siderite (FeCO₃)
(v) Goethite (FeO(OH))
(2aii)
(PICK ANY THREE)
(i) Environmental pollution.
(ii) Air pollution.
(iii) Water pollution.
(iv) Soil contamination.
(v) Skin irritation and burns.
(vi) Poisoning.
(vii) Respiratory diseases.
(viii) Death when improperly handled.
(ix) Damage to plants and animals.
(2bi)
Li > Na > K
(2bii)
(i) Electrons occupy the lowest energy level first (Aufbau principle).
(ii) The maximum number of electrons in a shell is 2n².
(iii) Orbitals are singly occupied before pairing (Hund’s rule).
(2ci)
Oxidizing agent Accepts electrons and causes oxidation. While Reducing agent Donates electrons and causes reduction.
(2cii)
(i) KOH → K⁺ + OH⁻
(ii) Pb(NO₃)₂ → Pb²⁺ + 2NO₃⁻
(iii) Na₂CO₃ → 2Na⁺ + CO₃²⁻
(2di)
(i) Anode: The anode is the electrode at which oxidation takes place, that is, where electrons are lost by ions or atoms during electrolysis.
(ii) Cathode: The cathode is the electrode at which reduction takes place, that is, where electrons are gained by ions during electrolysis.
(2dii)
Given:
I = 1.0 A
t = 15 min = 900 s
F = 96,500 C mol⁻¹
Molar volume at STP = 22.4 dm³
Q = It = 1.0 × 900 = 900 C
Moles of electrons = 900 / 96,500 = 0.00933 mol
2e⁻ produce 1 mole of H₂
Moles of H₂ = 0.00933 / 2 = 0.00466 mol
Volume of H₂ = 0.00466 × 22.4 = 0.104 dm³
Answer = 0.104 dm³
(3a)
Check the diagram below
(3bi)
(PICK ANY ONE)
(i) Endothermic reaction absorbs heat from the surroundings while Exothermic reaction releases heat to the surroundings.
(ii) Endothermic reaction has a positive enthalpy change (ΔH > 0) while Exothermic reaction has a negative enthalpy change (ΔH < 0).
(iii) Endothermic reaction makes the surroundings colder while Exothermic reaction makes the surroundings warmer.
(iv) Endothermic reaction requires a continuous supply of energy while Exothermic reaction gives out energy after it starts.
(v) Endothermic reaction has products with higher energy than the reactants while Exothermic reaction has products with lower energy than the reactants.
(vi) Endothermic reaction stores energy in the products while Exothermic reaction releases energy to the surroundings.
(vii) Endothermic reaction is represented by a positive heat change while Exothermic reaction is represented by a negative heat change.
(3bii)
Le Chatelier’s principle states that when a system at equilibrium is disturbed by a change in concentration, temperature, or pressure, the equilibrium shifts in a direction that opposes the change and establishes a new equilibrium.
(3biii)
(PICK ANY THREE)
(i) Change in concentration of reactants or products.
(ii) Change in temperature.
(iii) Change in pressure.
(iv) Change in volume (for gaseous systems).
(v) Addition of a catalyst (speeds attainment of equilibrium but does not change the equilibrium position).
(vi) Removal of a reactant.
(vii) Removal of a product.
(viii) Presence of an inert gas (may affect gaseous equilibria under constant pressure).
(3ci)
(i) Saturated solution: A saturated solution is a solution that contains the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature.
(ii) Molar solution: A molar solution is a solution containing one mole of solute dissolved in one cubic decimetre (1 dm³ or 1 litre) of solution.
(3cii)
Given:
Volume = 250 cm³ = 0.250 dm³
Concentration = 0.2 mol dm⁻³
Molar mass of Na₂CO₃
= (2 × 23) + 12 + (3 × 16)
= 46 + 12 + 48
= 106 g mol⁻¹
Number of moles
= C × V
= 0.2 × 0.250
= 0.05 mol
Mass
= Number of moles × Molar mass
= 0.05 × 106
= 5.3 g
∴ Mass of sodium trioxocarbonate (IV) required = 5.3 g.
(3di)
(i) Paper chromatography
(ii) 4 components
(iii) Chromatography paper (filter paper).
(iv) is the IV part
(3dii)
I: Filtration
II: Crystallization
(4ai)
A buffer solution is a solution that resists changes in pH when small amounts of acid or alkali are added or when it is diluted.
(4aii)
(PICK ANY TWO)
(i) It is used to maintain a constant pH in chemical reactions.
(ii) It is used in pharmaceutical preparations.
(iii) It is used in medical and clinical laboratories.
(iv) It is used in biological processes and enzyme reactions.
(v) It is used in the calibration of pH meters.
(vi) It is used in analytical chemistry during titrations.
(vii) It is used in the manufacture of cosmetics and food products to maintain a stable pH.
(4bi)
Haber process
(4bii)
(PICK ANY TWO)
(i) It is a colourless gas.
(ii) It is odourless.
(iii) It is tasteless.
(iv) It is slightly soluble (almost insoluble) in water.
(v) It is less dense than air.
(vi) It is a diatomic gas (N₂).
(vii) It has a low boiling point.
(4biii)
(i) Diamond
(ii) Graphite
(4biv)
(i) Diamond: Giant three-dimensional tetrahedral covalent structure.
(ii) Graphite: Giant layered hexagonal covalent structure.
(4bv)
(PICK ANY ONE)
(i) It is used as a fuel.
(ii) It is used for water purification.
(iii) It is used in gas masks to absorb poisonous gases.
(iv) It is used as a decolourising agent in the sugar industry.
(v) It is used for removing bad odours.
(vi) It is used in the manufacture of gunpowder.
(4ci)
I: Alkenes: CₙH₂ₙ
II: Alkynes: CₙH₂ₙ₋₂
(4cii)
(i) CH₃–CH₂–CH₂–CH₃
(ii) CH₃–CH(CH₃)–CH₃
(4ciii)
(i) Butane
(ii) 2-Methylpropane
(4civ)
Given:
Carbon = 60%
Hydrogen = 13.3%
Oxygen = 20.7%
Molar mass = 60
Number of moles:
C = 66/12 = 5.5
H = 13.3/1 = 13.3
O = 20.7/16 = 1.29
Divide by the smallest (1.29):
C = 5.5/1.29 ≈ 4
H = 13.3/1.29 ≈ 10
O = 1.29/1.29 = 1
Empirical formula = C₄H₁₀O
Empirical formula mass = (4 × 12) + (10 × 1) + 16
= 48 + 10 + 16
= 74
∴ the molecular formula is C₄H₁₀O.
(5ai)
Octane rating is the measure of the ability of petrol (gasoline) to resist knocking or premature ignition in an internal combustion engine.
(5aii)
(PICK ANY TWO)
(i) Cracking breaks large hydrocarbon molecules into smaller molecules, while reforming rearranges the structure of hydrocarbon molecules without reducing the number of carbon atoms.
(ii) Cracking produces alkanes and alkenes, while reforming produces branched-chain, cyclic or aromatic hydrocarbons.
(iii) Cracking increases the quantity of petrol, while reforming improves the quality (octane rating) of petrol.
(iv) Cracking reduces the molecular size of hydrocarbons, while reforming changes only the molecular structure.
(v) Cracking mainly produces unsaturated hydrocarbons, while reforming mainly produces branched-chain and aromatic hydrocarbons.
(vi) Cracking is used to convert heavy petroleum fractions into lighter fractions, while reforming is used to convert straight-chain hydrocarbons into branched-chain hydrocarbons.
(vii) Cracking aims to increase the yield of useful fuels, while reforming aims to improve fuel performance by increasing its octane number.
(5bi)
Draw the diagram
(5bii)
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)
(5biii)
(PICK ANY TWO)
(i) It is used in fire extinguishers.
(ii) It is used in the manufacture of carbonated (soft) drinks.
(iii) It is used by green plants during photosynthesis.
(iv) It is used as a refrigerant in the form of dry ice.
(v) It is used in greenhouses to promote plant growth.
(5ci)
Vulcanization is the process of heating natural rubber with sulphur to improve its strength, elasticity and durability.
(5cii)
I: Natural rubber
(PICK ANY ONE)
(i) Latex
(ii) Smoked sheet rubber
(iii) Crepe rubber
(iv) Ribbed smoked sheet (RSS) rubber
(v) Pale crepe rubber
(vi) Technically Specified Natural Rubber
II: Synthetic rubber
(PICK ANY ONE)
(i) Neoprene
(ii) Buna-S (Styrene-Butadiene Rubber, SBR)
(iii) Buna-N (Nitrile Rubber, NBR)
(iv) Butyl rubber (IIR)
(v) Silicone rubber
(vi) Thiokol (Polysulphide rubber)
(5ciii)
Given:
Solubility of NaCl at 100°C = 39.8g per 100g of water
Solubility of NaCl at 15°C = 35.9
g per 100 g of water
Mass of water = 80g
At 100°C:
39.8/100 × 80 = 31.84g
At 15°C:
35.9/100 × 80 = 28.72 g
Mass of NaCl precipitated
= 31.84 − 28.72
= 3.12 g
∴ Mass of sodium chloride precipitated = 3.12 g.
NECO Chemistry Exam Date 2026
The National Examinations Council (NECO) has scheduled the 2026 Chemistry Examination as follows:
| Subject | Date | Time |
|---|---|---|
| Chemistry (Essay & Objective) | Tuesday, 14th July 2026 | 10:00 am – 1:00 pm |
Candidates are advised to arrive at their examination centres at least 30 minutes before the commencement of the examination.
Before leaving for the examination centre, ensure you have the following approved materials:
- Blue or black ink pen
- HB pencil
- Eraser
- Ruler
- Scientific calculator
- Sharpener
The Chemistry examination consists of both Objective (OBJ) and Essay (Theory) sections. Candidates should manage their time effectively to complete all required questions within the allotted time.
NECO Chemistry Questions and Answers 2026 OBJ
Below are some likely NECO Chemistry Objective Questions and Answers for the 2026 examination. Candidates are encouraged to practice these questions together with past questions for better preparation.
1. The smallest particle of an element that retains its chemical properties is called ______.
A. Molecule
B. Atom
C. Ion
D. Compound
Answer: B (Atom)
2. Which of the following is an acid?
A. Sodium hydroxide
B. Calcium oxide
C. Hydrochloric acid
D. Ammonia
Answer: C (Hydrochloric acid)
3. The chemical symbol for sodium is ______.
A. So
B. Sd
C. Na
D. Sn
Answer: C (Na)
4. Which gas is evolved when zinc reacts with dilute hydrochloric acid?
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Chlorine
Answer: C (Hydrogen)
5. The pH value of a neutral solution is ______.
A. 0
B. 5
C. 7
D. 14
Answer: C (7)
6. Which of the following is a noble gas?
A. Oxygen
B. Nitrogen
C. Helium
D. Hydrogen
Answer: C (Helium)
7. Rusting is an example of ______.
A. Neutralization
B. Oxidation
C. Distillation
D. Sublimation
Answer: B (Oxidation)
8. The instrument used to measure the acidity or alkalinity of a solution is a ______.
A. Thermometer
B. Burette
C. pH meter
D. Pipette
Answer: C (pH meter)
9. Which of the following is an example of an organic compound?
A. Sodium chloride
B. Methane
C. Water
D. Ammonia
Answer: B (Methane)
10. The process of coating iron with zinc to prevent rusting is known as ______.
A. Electrolysis
B. Galvanization
C. Distillation
D. Polymerization
Answer: B (Galvanization)
More verified NECO Chemistry Objective Questions and Answers will be updated on this page before the examination.
NECO Chemistry Questions and Answers 2026 Essay
Below are likely NECO Chemistry Essay Questions and Answers for the 2026 Senior School Certificate Examination (SSCE). Candidates are advised to study these questions together with the NECO syllabus and past questions for effective preparation.
Question 1
Define an acid and a base.
Answer:
An acid is a substance that produces hydrogen ions (H+) when dissolved in water.
A base is a substance that produces hydroxide ions (OH–) when dissolved in water or accepts hydrogen ions during a chemical reaction.
Question 2
State five differences between ionic bonding and covalent bonding.
Answer:
| Ionic Bond | Covalent Bond |
|---|---|
| Formed by transfer of electrons. | Formed by sharing of electrons. |
| Occurs mainly between metals and non-metals. | Occurs mainly between non-metals. |
| Has high melting and boiling points. | Usually has lower melting and boiling points. |
| Conducts electricity when molten or in solution. | Generally does not conduct electricity. |
| Produces ions. | Produces molecules. |
Question 3
Explain electrolysis.
Answer:
Electrolysis is the chemical decomposition of an electrolyte by the passage of electric current through its molten or aqueous solution.
Electrolysis is widely used in electroplating, purification of metals, extraction of reactive metals, and industrial chemical production.
Question 4
State five physical properties of acids.
Answer:
- They have a sour taste.
- They turn blue litmus paper red.
- They react with metals to produce hydrogen gas.
- They conduct electricity in aqueous solution.
- They react with bases to form salt and water.
Area of concentration for chemistry NECO 2026
Candidates preparing for NECO Chemistry should pay special attention to topics that are frequently tested in previous examinations.
Major Topics
- Atomic Structure
- Periodic Table
- Chemical Bonding
- Acids, Bases and Salts
- Electrolysis
- Organic Chemistry
- Gas Laws
- Stoichiometry
- Redox Reactions
- Chemical Equilibrium
- Environmental Chemistry
- Qualitative Analysis
- Water and Air
- Separation Techniques
These topics have consistently appeared in both the objective and essay sections of previous NECO Chemistry examinations.
Frequently Repeated Areas
- Balancing chemical equations
- Mole calculations
- Periodic table trends
- Acid-base reactions
- Electrolysis
- Organic compounds
- Gas laws
Important Chemistry Formulas and Definitions
Candidates should master the following Chemistry formulas and scientific definitions before the examination.
Common Chemistry Formulas
| Concept | Formula |
|---|---|
| Density | Density = Mass ÷ Volume |
| Molarity | Molarity = Number of Moles ÷ Volume of Solution (L) |
| Percentage Purity | (Mass of Pure Substance ÷ Total Mass) × 100% |
| Percentage Yield | (Actual Yield ÷ Theoretical Yield) × 100% |
| Relative Density | Density of Substance ÷ Density of Water |
| Number of Moles | Mass ÷ Molar Mass |
| Ideal Gas Equation | PV = nRT |
Important Definitions
- Atom: The smallest particle of an element that retains its chemical properties.
- Molecule: Two or more atoms chemically combined.
- Ion: An atom or group of atoms carrying an electrical charge.
- Mole: The amount of substance containing 6.02 × 1023 particles.
- Catalyst: A substance that speeds up a chemical reaction without being consumed.
Understanding these formulas and definitions will help candidates answer both objective and essay questions confidently during the examination.
Chemistry Examination Instructions
Candidates sitting for the NECO Chemistry Examination 2026 should carefully read and follow all examination instructions to maximize their performance and avoid unnecessary mistakes.
The Chemistry paper consists of Objective (OBJ) and Essay (Theory) sections. Candidates are expected to answer all objective questions and the required number of essay questions within the allocated time.
Important Examination Guidelines
- Arrive at the examination centre at least 30 minutes before the examination begins.
- Come with all approved writing materials, including blue or black ink pens, HB pencil, ruler, eraser, and a scientific calculator.
- Read every instruction on the question paper carefully before attempting any question.
- Show all calculations clearly in the essay section, as marks are often awarded for correct working.
- Always write balanced chemical equations where required.
- State the correct SI units in all calculation questions.
- Manage your examination time properly by allocating enough time to both the objective and essay sections.
- Review your answers before submitting your answer booklet.
- Avoid every form of examination malpractice and comply with all NECO examination regulations.
Following these instructions carefully can help candidates avoid unnecessary loss of marks and improve their overall performance.
How to Score High in NECO Chemistry 2026
Chemistry is one of the highest-scoring science subjects for candidates who prepare consistently and understand the basic concepts. The following tips can help you achieve an excellent grade.
1. Study the NECO Chemistry Syllabus
Use the official syllabus as your study guide to ensure you cover all examinable topics before the examination.
2. Master Important Chemistry Formulas
Learn and practice important formulas involving moles, molarity, gas laws, density, percentage yield, and concentration.
3. Practice Balancing Chemical Equations
Balancing equations is an important aspect of Chemistry and is frequently tested in both objective and essay questions.
4. Study Past Questions
Practising previous NECO Chemistry questions helps you understand the examination pattern and identify commonly repeated topics.
5. Understand Practical Chemistry
Revise laboratory apparatus, qualitative analysis, titration, separation techniques, and experimental procedures, as practical knowledge often supports theory questions.
6. Revise the Periodic Table
Understand the properties, symbols, groups, periods, and trends of elements in the periodic table.
7. Practice Calculation Questions Daily
Many Chemistry questions involve calculations. Regular practice will improve both your speed and accuracy.
Consistent revision, understanding of concepts, and regular practice remain the best strategies for scoring an A1 in NECO Chemistry.
Conclusion
The NECO Chemistry 2026 is one of the most important science subjects for candidates seeking admission into universities, polytechnics, colleges of education, and other higher institutions. A good grade in Chemistry is often required for courses such as Medicine, Nursing, Pharmacy, Engineering, Biochemistry, Microbiology, Agriculture, and other science-related programmes.
To perform excellently in the examination, candidates should begin their preparation early by studying the official NECO Chemistry syllabus, revising class notes, practicing past questions, and mastering important formulas, definitions, and calculations.
Candidates should pay special attention to frequently tested topics such as:
- Atomic Structure
- Periodic Table
- Chemical Bonding
- Acids, Bases and Salts
- Electrolysis
- Stoichiometry
- Organic Chemistry
- Gas Laws
- Redox Reactions
- Qualitative Analysis
In addition to revising theory, candidates should also understand practical Chemistry concepts because many essay questions are based on laboratory experiments, qualitative analysis, titration, and chemical calculations.
Important Reminder: This article is designed as a revision guide to support your preparation. For the best results, combine it with your class notes, recommended textbooks, practical manuals, the official NECO syllabus, and past examination questions.
As the examination date approaches, we will continue updating this page with more verified NECO Chemistry Objective (OBJ) and Essay Questions, detailed solutions, revision materials, and examination tips to help candidates prepare effectively.
We encourage all candidates to bookmark this page and visit regularly for the latest updates before the examination.
We wish every NECO candidate success in the 2026 Chemistry Examination.
If you found this guide helpful, kindly share it with your classmates, friends, and other NECO candidates preparing for the examination through Facebook, WhatsApp, Telegram, and other social media platforms.
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