Chemistry is the second most tested academic subject in AFNS after Biology. These 40 solved MCQs cover the exact topics that appear repeatedly — with explanations, not just answer keys.
Also study: AFNS Biology MCQs | AFNS Physics MCQs | Full AFNS Syllabus 2026
Section 1: Atomic Structure
Q1. The atomic number of an element equals:
A) Number of neutrons B) Number of protons C) Mass number D) Number of electrons + neutrons
✅ Answer: B — Number of protons
Atomic number = number of protons in the nucleus. In a neutral atom, it also equals the number of electrons.
Q2. Isotopes are atoms of the same element with different:
A) Atomic number B) Number of protons C) Number of neutrons D) Chemical properties
✅ Answer: C — Number of neutrons
Isotopes have the same atomic number (protons) but different mass numbers due to different neutron counts. Example: Carbon-12 and Carbon-14.
Q3. The mass number of an atom is:
A) Protons only B) Neutrons only C) Protons + Neutrons D) Protons + Electrons
✅ Answer: C — Protons + Neutrons
Mass number = protons + neutrons. Electrons have negligible mass and are not included.
Q4. Which subatomic particle has no charge?
A) Proton B) Electron C) Neutron D) Ion
✅ Answer: C — Neutron
Protons are positive (+1), electrons are negative (−1), neutrons are neutral (0).
Q5. Valency of an element depends on:
A) Mass number B) Number of electrons in outermost shell C) Number of neutrons D) Atomic radius
✅ Answer: B — Number of electrons in outermost shell
Valency = number of electrons gained, lost, or shared to achieve stable configuration (usually 8 electrons — octet rule).
Section 2: Chemical Bonding
Q6. Ionic bonds form between:
A) Two non-metals B) A metal and non-metal C) Two metals D) Noble gases
✅ Answer: B — Metal and non-metal
Ionic bonds form when a metal donates electrons to a non-metal. Example: NaCl (sodium chloride/table salt).
Q7. Water molecule (H₂O) has what type of bond?
A) Ionic B) Covalent C) Metallic D) Hydrogen
✅ Answer: B — Covalent
Hydrogen and Oxygen share electrons — covalent bond. However, water also has hydrogen bonds between molecules, which explain its high boiling point.
Q8. Which of the following is NOT a property of ionic compounds?
A) High melting point B) Conduct electricity when dissolved C) Low boiling point D) Soluble in water
✅ Answer: C — Low boiling point
Ionic compounds have HIGH melting and boiling points due to strong electrostatic forces between ions.
Section 3: Acids, Bases & Salts
Q9. The pH of pure water is:
A) 0 B) 7 C) 14 D) 5
✅ Answer: B — 7
Pure water is neutral (pH = 7). Below 7 is acidic, above 7 is basic/alkaline. This is among the most frequently tested chemistry facts in AFNS.
Q10. Which acid is present in the human stomach?
A) Sulphuric acid B) Nitric acid C) Hydrochloric acid D) Acetic acid
✅ Answer: C — Hydrochloric acid (HCl)
HCl in gastric juice activates pepsin and kills bacteria. Excess HCl causes acidity/peptic ulcers.
Q11. Neutralisation reaction produces:
A) Acid + Base B) Salt + Water C) Oxide + Water D) Gas + Salt
✅ Answer: B — Salt + Water
Acid + Base → Salt + Water. Example: HCl + NaOH → NaCl + H₂O
Q12. Vinegar contains which acid?
A) Citric acid B) Lactic acid C) Acetic acid D) Tartaric acid
✅ Answer: C — Acetic acid (ethanoic acid)
Vinegar is 4–8% acetic acid (CH₃COOH). Citric acid is in lemons; lactic acid in milk; tartaric acid in grapes.
Q13. A strong acid compared to a weak acid:
A) Partially dissociates B) Fully dissociates in water C) Has higher pH D) Is less corrosive
✅ Answer: B — Fully dissociates in water
Strong acids (HCl, H₂SO₄, HNO₃) completely ionise. Weak acids (acetic acid, carbonic acid) partially ionise, establishing an equilibrium.
Section 4: Periodic Table
Q14. Elements in the same group of the periodic table have:
A) Same mass number B) Same number of electron shells C) Same number of valence electrons D) Same atomic mass
✅ Answer: C — Same number of valence electrons
Elements in the same group share the same number of outer shell electrons, giving them similar chemical properties.
Q15. Noble gases are found in Group:
A) I B) VII C) VIII / 18 D) IV
✅ Answer: C — Group 18 (VIII)
Noble gases (He, Ne, Ar, Kr, Xe, Rn) are in Group 18. They are chemically inert because their outermost shell is full.
Q16. Which is the most electronegative element?
A) Oxygen B) Chlorine C) Nitrogen D) Fluorine
✅ Answer: D — Fluorine
Fluorine has the highest electronegativity (3.98 on Pauling scale). Electronegativity increases across a period and up a group.
Section 5: Organic Chemistry
Q17. The simplest hydrocarbon is:
A) Ethane B) Propane C) Methane D) Butane
✅ Answer: C — Methane (CH₄)
Methane is the first alkane (1 carbon). It is the main component of natural gas.
Q18. Functional group of alcohols is:
A) −COOH B) −OH C) −CHO D) −NH₂
✅ Answer: B — −OH (hydroxyl group)
Alcohols contain −OH group. −COOH is carboxylic acid, −CHO is aldehyde, −NH₂ is amine.
Q19. Fermentation of glucose produces:
A) Methane + H₂O B) Ethanol + CO₂ C) Acetic acid + H₂ D) Lactic acid + O₂
✅ Answer: B — Ethanol + CO₂
Yeast ferments glucose anaerobically: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. This is used in bread-making (CO₂ causes rising) and alcohol production.
Q20. Which is an example of an addition reaction?
A) CH₄ + Cl₂ → CH₃Cl + HCl B) C₂H₄ + H₂ → C₂H₆ C) C₂H₆ → C₂H₄ + H₂ D) NaCl + H₂O → NaOH + HCl
✅ Answer: B — C₂H₄ + H₂ → C₂H₆
Addition reactions occur in unsaturated compounds (alkenes/alkynes). H₂ is added across the double bond, converting ethene to ethane.
Section 6: Biomolecules & Applied Chemistry
Q21. Carbohydrates are made of:
A) C, H, N B) C, H, O C) C, H, O, N D) C, N, O
✅ Answer: B — Carbon, Hydrogen, Oxygen
Carbohydrates (sugars and starches) contain C, H, O in ratio approximately 1:2:1. Proteins additionally contain Nitrogen.
Q22. Glucose formula is:
A) C₁₂H₂₂O₁₁ B) C₆H₁₂O₆ C) C₆H₆O₆ D) C₂H₅OH
✅ Answer: B — C₆H₁₂O₆
Glucose (simple sugar/monosaccharide) = C₆H₁₂O₆. Sucrose (table sugar) = C₁₂H₂₂O₁₁. Ethanol = C₂H₅OH.
Q23. Saponification is the process of making:
A) Vinegar B) Soap C) Plastic D) Fertiliser
✅ Answer: B — Soap
Saponification = hydrolysis of fat/oil with NaOH or KOH to produce glycerol + soap (sodium/potassium salts of fatty acids).
Q24. Rusting of iron is an example of:
A) Reduction B) Combustion C) Oxidation D) Hydration
✅ Answer: C — Oxidation
Iron reacts with oxygen and water to form iron oxide (rust): 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃. Iron loses electrons — this is oxidation.
Q25. Which gas is used in fire extinguishers?
A) Oxygen B) Nitrogen C) Carbon dioxide D) Hydrogen
✅ Answer: C — Carbon dioxide (CO₂)
CO₂ is denser than air and smothers fire by cutting off oxygen supply. It does not conduct electricity, making it safe for electrical fires.
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FAQs
What chemistry topics come in AFNS test?
Most repeated AFNS chemistry topics are atomic structure, chemical bonding, acids and bases (pH, neutralisation), periodic table trends, basic organic chemistry (hydrocarbons, functional groups, fermentation), and biomolecules (carbohydrates, lipids).
How many chemistry questions are in AFNS?
Chemistry typically makes up approximately 15% of the AFNS academic MCQs, making it the third most important subject after Biology and Verbal Intelligence.
