Chemistry MCQs – 50 Solved Questions for PPSC, FPSC & NTS

Chemistry MCQs form a fixed part of PPSC, FPSC, NTS, ETEA, FGEI and one-paper exams, and the same topics return every year: chemical formulas, symbols, acids and bases, atomic structure and everyday chemistry. This guide gives you 50 solved Chemistry MCQs with short explanations, organised so that the high-yield formulas and symbols sit together in one revision session.

How to use: Attempt each question on paper in under one minute, then read the explanation. Units, formulas and definitions repeat more than anything else in these papers.

Most Repeated Chemistry MCQs for PPSC, FPSC & NTS Topics

Chemical formulas — water, CO₂, ammonia, sulfuric acid, glucose
Symbols from Latin names — Na, K, Fe, Ca
Acids and bases — pH, neutralisation, common acids in food
Atomic structure — atomic number, mass number, valency, ions
Gases and their tests — CO₂ and limewater, hydrogen pop test
Physical vs chemical change — the classic board question
Everyday chemistry — rusting, baking soda, fire extinguishers

50 Solved MCQs

Q1. The chemical formula of common table salt is:

A) KCl

B) NaCl

C) CaCl₂

D) MgCl₂

Answer: B) NaCl

Explanation: Sodium chloride — sodium gives up one electron and chlorine accepts one.

Q2. The atomic number of carbon is:

A) 6

B) 4

C) 8

D) 12

Answer: A) 6

Explanation: Carbon has 6 protons; its mass number is 12.

Q3. The most abundant gas in Earth’s atmosphere is:

A) Oxygen

B) Nitrogen

C) Carbon dioxide

D) Argon

Answer: B) Nitrogen

Explanation: Nitrogen makes about 78% of the atmosphere; oxygen about 21%.

Q4. The pH of pure water at 25°C is:

A) 5

B) 7

C) 6

D) 8

Answer: B) 7

Explanation: Pure water is neutral, with equal H⁺ and OH⁻ concentrations.

Q5. Which acid is present in lemon juice?

A) Acetic acid

B) Formic acid

C) Lactic acid

D) Citric acid

Answer: D) Citric acid

Explanation: Citrus fruits contain citric acid, a weak organic acid.

Q6. The chemical symbol for sodium is:

A) So

B) Sd

C) Na

D) N

Answer: C) Na

Explanation: Na comes from the Latin name Natrium.

Q7. The chemical symbol for potassium is:

A) P

B) Po

C) Pt

D) K

Answer: D) K

Explanation: K comes from the Latin name Kalium.

Q8. Which gas is produced when a metal reacts with a dilute acid?

A) Hydrogen

B) Oxygen

C) Nitrogen

D) Carbon dioxide

Answer: A) Hydrogen

Explanation: Metal + acid → salt + hydrogen gas, which burns with a pop test.

Q9. The formula of carbon dioxide is:

A) CO₂

B) CO

C) C₂O

D) CO₃

Answer: A) CO₂

Explanation: One carbon atom bonded to two oxygen atoms.

Q10. Which one is a noble gas?

A) Chlorine

B) Nitrogen

C) Argon

D) Oxygen

Answer: C) Argon

Explanation: Group 18 elements such as helium, neon and argon have full outer shells.

Q11. Rusting of iron requires:

A) Oxygen and water

B) Only oxygen

C) Only water

D) Only acids

Answer: A) Oxygen and water

Explanation: Both oxygen and moisture are needed; salt accelerates the process.

Q12. The process of a solid turning directly into a gas is called:

A) Melting

B) Sublimation

C) Condensation

D) Evaporation

Answer: B) Sublimation

Explanation: Iodine and dry ice are classic examples of sublimation.

Q13. The atomic number of an element equals the number of:

A) Neutrons

B) Protons

C) Electrons in the outer shell

D) Nucleons

Answer: B) Protons

Explanation: Atomic number = number of protons, which also equals electrons in a neutral atom.

Q14. Which is a chemical change?

A) Melting of ice

B) Dissolving sugar in water

C) Boiling water

D) Rusting of iron

Answer: D) Rusting of iron

Explanation: Rusting creates a new substance; the others are physical changes.

Q15. The formula of ozone is:

A) O₂

B) O₃

C) O

D) O₄

Answer: B) O₃

Explanation: Ozone is a triatomic form of oxygen.

Q16. The lightest element is:

A) Helium

B) Hydrogen

C) Lithium

D) Carbon

Answer: B) Hydrogen

Explanation: Hydrogen has atomic number 1 and the lowest atomic mass.

Q17. Avogadro’s number is approximately:

A) 6.02 × 10²³

B) 3.14 × 10²³

C) 9.8 × 10²³

D) 1.6 × 10¹⁹

Answer: A) 6.02 × 10²³

Explanation: One mole of any substance contains 6.022 × 10²³ particles.

Q18. Which acid is present in the human stomach?

A) Sulfuric acid

B) Nitric acid

C) Acetic acid

D) Hydrochloric acid

Answer: D) Hydrochloric acid

Explanation: Hydrochloric acid (HCl) digests food and kills bacteria.

Q19. The hardest natural substance is:

A) Gold

B) Iron

C) Diamond

D) Quartz

Answer: C) Diamond

Explanation: Diamond scores 10 on the Mohs hardness scale.

Q20. Which gas turns limewater milky?

A) Carbon dioxide

B) Oxygen

C) Hydrogen

D) Nitrogen

Answer: A) Carbon dioxide

Explanation: CO₂ reacts with limewater to form insoluble calcium carbonate.

Q21. The valency of oxygen is:

A) 1

B) 3

C) 4

D) 2

Answer: D) 2

Explanation: Oxygen needs two electrons to complete its outer shell.

Q22. The chemical formula of water is:

A) HO

B) H₂O

C) H₂O₂

D) OH

Answer: B) H₂O

Explanation: Two hydrogen atoms bonded to one oxygen atom.

Q23. Which is an alkali metal?

A) Sodium

B) Calcium

C) Aluminium

D) Iron

Answer: A) Sodium

Explanation: Group 1 elements such as sodium, potassium and lithium are alkali metals.

Q24. The reaction of an acid with a base is called:

A) Oxidation

B) Reduction

C) Neutralisation

D) Combustion

Answer: C) Neutralisation

Explanation: Acid + base → salt + water.

Q25. Which gas is used in fire extinguishers?

A) Oxygen

B) Hydrogen

C) Carbon dioxide

D) Nitrogen

Answer: C) Carbon dioxide

Explanation: CO₂ smothers fire by cutting off oxygen.

Q26. The element with the symbol ‘Fe’ is:

A) Fluorine

B) Lead

C) Tin

D) Iron

Answer: D) Iron

Explanation: Fe comes from the Latin name Ferrum.

Q27. Which of the following is a mixture?

A) Water

B) Salt

C) Air

D) Carbon dioxide

Answer: C) Air

Explanation: Air contains several gases that are not chemically combined.

Q28. The formula of ammonia is:

A) NH₄

B) NH₃

C) NO₂

D) N₂O

Answer: B) NH₃

Explanation: One nitrogen bonded to three hydrogen atoms.

Q29. Concentration of a solution is expressed in:

A) Moles

B) Molarity

C) Volume

D) Density

Answer: B) Molarity

Explanation: Molarity = moles of solute per litre of solution.

Q30. Which substance is a good conductor of electricity?

A) Sugar solution

B) Pure water

C) Distilled water

D) Salt solution

Answer: D) Salt solution

Explanation: Dissolved salt provides free ions that carry current.

Q31. The atomic mass of oxygen is approximately:

A) 12

B) 16

C) 14

D) 20

Answer: B) 16

Explanation: Oxygen’s standard atomic weight is about 16.

Q32. Which gas is known as laughing gas?

A) Nitric oxide

B) Nitrous oxide

C) Nitrogen dioxide

D) Ammonia

Answer: B) Nitrous oxide

Explanation: Nitrous oxide (N₂O) is used as a mild anaesthetic.

Q33. The chemical name for baking soda is:

A) Sodium bicarbonate

B) Sodium chloride

C) Calcium carbonate

D) Sodium hydroxide

Answer: A) Sodium bicarbonate

Explanation: Sodium bicarbonate (NaHCO₃) releases CO₂ when heated or mixed with acid.

Q34. Which element has the symbol ‘Ca’?

A) Calcium

B) Carbon

C) Copper

D) Cadmium

Answer: A) Calcium

Explanation: Calcium is a Group 2 alkaline earth metal.

Q35. The process of electrolysis uses:

A) Heat energy

B) Electrical energy

C) Light energy

D) Sound energy

Answer: B) Electrical energy

Explanation: Electric current drives the decomposition of a compound.

Q36. Which is the most abundant metal in the Earth’s crust?

A) Aluminium

B) Iron

C) Copper

D) Gold

Answer: A) Aluminium

Explanation: Aluminium is the most abundant metal by mass in the crust.

Q37. The pH of a strong acid is generally:

A) Close to 7

B) Above 7

C) Exactly 14

D) Below 3

Answer: D) Below 3

Explanation: Strong acids have very low pH, typically below 3.

Q38. Which one is an exothermic reaction?

A) Combustion of fuel

B) Photosynthesis

C) Melting of ice

D) Dissolution of NH₄Cl

Answer: A) Combustion of fuel

Explanation: Combustion releases energy as heat and light.

Q39. The formula of sulfuric acid is:

A) HCl

B) HNO₃

C) CH₃COOH

D) H₂SO₄

Answer: D) H₂SO₄

Explanation: Sulfuric acid contains two hydrogen atoms, one sulfur and four oxygen atoms.

Q40. Which gas is released during photosynthesis?

A) Carbon dioxide

B) Nitrogen

C) Hydrogen

D) Oxygen

Answer: D) Oxygen

Explanation: Plants absorb CO₂ and release O₂.

Q41. An atom that gains electrons becomes:

A) A cation

B) Isotope

C) An anion

D) Neutral

Answer: C) An anion

Explanation: Gaining electrons creates a negative ion, an anion.

Q42. The number of electrons in a neutral sodium atom is:

A) 10

B) 12

C) 23

D) 11

Answer: D) 11

Explanation: Sodium’s atomic number is 11, so a neutral atom has 11 electrons.

Q43. Which is a noble metal used in jewellery?

A) Gold

B) Iron

C) Copper

D) Zinc

Answer: A) Gold

Explanation: Gold is highly unreactive, making it ideal for jewellery.

Q44. The chemical formula for glucose is:

A) C₆H₁₂O₆

B) C₂H₆O

C) CH₄

D) C₆H₆

Answer: A) C₆H₁₂O₆

Explanation: Glucose is a six-carbon sugar with 12 hydrogen and 6 oxygen atoms.

Q45. Which type of bond forms between Na and Cl?

A) Covalent

B) Metallic

C) Ionic

D) Hydrogen

Answer: C) Ionic

Explanation: Sodium donates an electron to chlorine, forming an ionic bond.

Q46. Rusting is an example of:

A) Reduction

B) Neutralisation

C) Oxidation

D) Sublimation

Answer: C) Oxidation

Explanation: Iron loses electrons to oxygen, an oxidation reaction.

Q47. The element with atomic number 1 is:

A) Helium

B) Lithium

C) Carbon

D) Hydrogen

Answer: D) Hydrogen

Explanation: Hydrogen has one proton.

Q48. Which one is not a compound?

A) Water

B) Salt

C) Oxygen gas

D) Carbon dioxide

Answer: C) Oxygen gas

Explanation: Oxygen gas exists as O₂ molecules of a single element.

Q49. Lime water is a solution of:

A) Sodium hydroxide

B) Potassium hydroxide

C) Calcium hydroxide

D) Ammonium hydroxide

Answer: C) Calcium hydroxide

Explanation: Calcium hydroxide solution is used to test for carbon dioxide.

Q50. The molecular mass of water is approximately:

A) 16

B) 20

C) 18

D) 22

Answer: C) 18

Explanation: Two hydrogens (2) plus one oxygen (16) equals 18.

Most Repeated Chemistry MCQs for PPSC, FPSC & NTS Topics

50 Solved MCQs

Q1. The chemical formula of common table salt is:

Q2. The atomic number of carbon is:

Q3. The most abundant gas in Earth’s atmosphere is:

Q4. The pH of pure water at 25°C is:

Q5. Which acid is present in lemon juice?

Q6. The chemical symbol for sodium is:

Q7. The chemical symbol for potassium is:

Q8. Which gas is produced when a metal reacts with a dilute acid?

Q9. The formula of carbon dioxide is:

Q10. Which one is a noble gas?

Q11. Rusting of iron requires:

Q12. The process of a solid turning directly into a gas is called:

Q13. The atomic number of an element equals the number of:

Q14. Which is a chemical change?

Q15. The formula of ozone is:

Q16. The lightest element is:

Q17. Avogadro’s number is approximately:

Q18. Which acid is present in the human stomach?

Q19. The hardest natural substance is:

Q20. Which gas turns limewater milky?

Q21. The valency of oxygen is:

Q22. The chemical formula of water is:

Q23. Which is an alkali metal?

Q24. The reaction of an acid with a base is called:

Q25. Which gas is used in fire extinguishers?

Q26. The element with the symbol ‘Fe’ is:

Q27. Which of the following is a mixture?

Q28. The formula of ammonia is:

Q29. Concentration of a solution is expressed in:

Q30. Which substance is a good conductor of electricity?

Q31. The atomic mass of oxygen is approximately:

Q32. Which gas is known as laughing gas?

Q33. The chemical name for baking soda is:

Q34. Which element has the symbol ‘Ca’?

Q35. The process of electrolysis uses:

Q36. Which is the most abundant metal in the Earth’s crust?

Q37. The pH of a strong acid is generally:

Q38. Which one is an exothermic reaction?

Q39. The formula of sulfuric acid is:

Q40. Which gas is released during photosynthesis?

Q41. An atom that gains electrons becomes:

Q42. The number of electrons in a neutral sodium atom is:

Q43. Which is a noble metal used in jewellery?

Q44. The chemical formula for glucose is:

Q45. Which type of bond forms between Na and Cl?

Q46. Rusting is an example of:

Q47. The element with atomic number 1 is:

Q48. Which one is not a compound?

Q49. Lime water is a solution of:

Q50. The molecular mass of water is approximately:

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