Metals, Non-Metals and Reactivity Series – NDA Chemistry PYQs

Solve NDA Chemistry previous-year questions on Metals, Non-Metals and Reactivity with detailed solutions and explanations.

Chapter-wise PYQs • Concept-based explanations • Exam insights

NDA 2026-II

Q. 1. Consider the following statements :

I. Zinc metal, when treated with both HCl (aq.) and NaOH (aq.) separately, produces molecular hydrogen.

II. An aqueous copper sulphate solution cannot be kept in a zinc vessel.

III. Lemon, tamarind and tomato are natural sources of citric acid, oxalic acid and tartaric acid, respectively.

Which of the statements given above are correct ?

(a) I and II only

(b) II and III only

(d) I, II and III

Answer: (a) I and II only

Explanation: Statement I: Correct – Zn + 2HCl → ZnCl₂ + H₂↑ (reaction with acid); Zn + 2NaOH + 2H₂O → Na₂[Zn(OH)₄] + H₂↑ (reaction with alkali). Both produce H₂. Statement II: Correct – Zn is more reactive than Cu; Zn displaces Cu from CuSO₄, so the vessel would dissolve. Statement III: Incorrect – tamarind contains tartaric acid; tomato contains oxalic/citric acid. The assignment of oxalic acid to tamarind and tartaric acid to tomato is reversed. Only I and II are correct. Concept Tested: Amphoteric nature of zinc; reactivity; natural organic acids

NDA 2023-II

Q. 2. Galvanization is a method of protecting iron from rusting by coating with a thin layer of

(a) Gallium

(b) Aluminum

(d) Silver

Answer: (c) Zinc

Explanation: Galvanization = coating iron or steel with zinc. The zinc acts as a protective barrier and as a sacrificial anode. “Galvanized iron” is widely used in roofing and pipes. Concept Tested: Galvanization – zinc coating on iron

Q. 3. Which one of the following metals does NOT react with cold water to liberate hydrogen gas ?

(a) Potassium

(b) Iron

(d) Sodium

Answer: (b) Iron

Explanation: Iron does not react with cold water under normal conditions. Iron reacts only with steam to form Fe₃O₄ and H₂. Potassium, sodium and calcium all react vigorously with cold water to liberate H₂. Concept Tested: Metals not reacting with cold water – iron

Q. 4. Which one of the following metals can be extracted using carbon as reducing agent ?

(a) Zinc

(b) Silver

(d) Aluminum

Answer: (a) Zinc

Explanation: Carbon can reduce oxides of metals that are less reactive than carbon in the activity series. Zinc is extracted from ZnO using carbon (coke): ZnO + C → Zn + CO. Silver and gold are obtained by other methods. Aluminium is more reactive than carbon and cannot be reduced by it. Concept Tested: Extraction of metals by carbon reduction – zinc

NDA 2023-I

Q. 5. Which one of the following is the correct arrangement of metals in the decreasing order of their reactivity ?

(a) Iron, Sodium, Silver, Copper

(b) Silver, Copper, Iron, Sodium

(d) Sodium, Iron, Copper, Silver

Answer: (d) Sodium, Iron, Copper, Silver

Explanation: Reactivity order (most reactive first): Na > Fe > Cu > Ag. Sodium is extremely reactive (Group 1). Iron is moderately reactive. Copper is less reactive. Silver is at the bottom of common metals’ reactivity. So the decreasing order is Sodium > Iron > Copper > Silver. Concept Tested: Reactivity series – Na > Fe > Cu > Ag in decreasing order

NDA 2022-II

Q. 6. Which one of the following is the correct reactivity series with water?

(a) Zinc > Iron > Lead > Copper

(b) Copper > Lead > Zinc > Iron

(d) Zinc > Copper > Iron > Lead

Answer: (a) Zinc > Iron > Lead > Copper

Explanation: Among these metals, reactivity with water in decreasing order: Zn > Fe > Pb > Cu. Zinc and iron react with steam. Lead barely reacts. Copper does not react with water. So (a) Zinc > Iron > Lead > Copper is correct. Concept Tested: Reactivity with water – Zn > Fe > Pb > Cu

Q. 7. Which one of the following metals floats in cold water?

(a) Magnesium

(b) Calcium

(d) Copper

Answer: (c) Potassium

Explanation: Potassium (density ≈ 0.86 g/cm³) is less dense than water and floats on it. It also reacts violently with cold water, often catching fire. Sodium also floats. Calcium sinks in water but reacts. Magnesium barely reacts with cold water. Copper sinks and does not react. Concept Tested: Density of potassium – floats on water

Q. 8. Silver artefacts get tarnished in air due to the formation of

(a) silver chloride

(b) silver oxide

(d) silver sulphate

Answer: (c) silver sulphide

Explanation: Silver reacts with hydrogen sulphide (H₂S) in air to form silver sulphide (Ag₂S), which is black. This causes the familiar darkening (tarnishing) of silverware. AgCl is white, Ag₂O is dark brown, Ag₂SO₄ is white – none cause the characteristic black tarnish. Concept Tested: Tarnishing of silver – silver sulphide Ag₂S formation

NDA 2021-II

Q. 9. To protect steel and iron from rusting, a thin layer of which one of the following metals is applied?

(a) Magnesium

(b) Zinc

(d) Lead

Answer: (b) Zinc

Explanation: Galvanization is the process of coating iron/steel with zinc to protect it from rusting. Zinc forms a protective oxide layer and acts as a sacrificial anode. This is the most common method of protecting iron from corrosion. Concept Tested: Galvanization – zinc coating to prevent rusting

Q. 10. Cinnabar is an ore of which one of the following?

(a) Copper

(b) Zinc

(d) Manganese

Answer: (c) Mercury

Explanation: Cinnabar (HgS) is the most important ore of mercury. It is a bright red mineral. Mercury is extracted from cinnabar by roasting in air: HgS + O₂ → Hg + SO₂. Concept Tested: Ore of mercury – cinnabar (HgS)

NDA 2021-I

Q. 11. Which one of the following reactions does not result in the evolution of hydrogen gas?

(a) Reaction of zinc metal with dilute sulphuric acid solution

(b) Mixing water to Plaster of Paris

(d) Reaction of potassium metal with water

Answer: (b) Mixing water to Plaster of Paris

Explanation: Plaster of Paris (CaSO₄·½H₂O) + water → gypsum (CaSO₄·2H₂O). This is a setting reaction – no hydrogen is evolved. Zn + H₂SO₄ → ZnSO₄ + H₂↑. Zn + NaOH + H₂O → Na₂[Zn(OH)₄] + H₂↑. K + H₂O → KOH + H₂↑. Concept Tested: Reactions that do not produce H₂ – Plaster of Paris setting

NDA 2020

Q. 12. Which one of the following represents the correct order of electron releasing tendency of metals?

(a) Zn > Cu > Ag

(b) Ag > Cu > Zn

(d) Cu > Ag > Zn

Answer: (a) Zn > Cu > Ag

Explanation: Same question as NDA 2019-II Q90. Zn > Cu > Ag is the correct reactivity/electron-releasing order. This repeated appearance confirms it is a high-frequency concept. Concept Tested: Electron releasing tendency – Zn > Cu > Ag (repeated question)

★ JOVIK Exam Insight: This question appeared in NDA 2019-II and NDA 2020 with identical wording and answer. Zn > Cu > Ag in the reactivity series is a reliable NDA fact.

NDA 2019-II

Q. 13. Which one of the following represents the correct order of electron releasing tendency of metals?

(a) Zn > Cu > Ag

(b) Ag > Cu > Zn

(d) Cu > Ag > Zn

Answer: (a) Zn > Cu > Ag

Explanation: Electron releasing tendency corresponds to position in the reactivity/electrochemical series. Higher up = more reactive = more tendency to release electrons. Zn > Cu > Ag in reactivity, so Zn has the highest electron releasing tendency. Concept Tested: Electrochemical series – electron releasing tendency Zn > Cu > Ag

NDA 2019-I

Q. 14. Which one of the following metals does NOT react with cold water?

(a) Calcium (Ca)

(b) Potassium (K)

(d) Sodium (Na)

Answer: (c) Magnesium (Mg)

Explanation: Ca, K and Na react vigorously with cold water. Magnesium does not react appreciably with cold water – it reacts very slowly (the oxide layer prevents reaction). Mg does react with steam to produce MgO and H₂. Concept Tested: Reaction of metals with cold water – Mg does not react

Q. 15. On exposure to moist air, copper gains a green coat on its surface due to formation of which one of the following compounds?

(a) Copper carbonate

(b) Copper oxide

(d) Copper nitrate

Answer: (a) Copper carbonate

Explanation: The green patina on copper (verdigris) is primarily basic copper carbonate: Cu₂(OH)₂CO₃. It forms when copper reacts with CO₂, H₂O and O₂ in moist air. This is what gives copper rooftops and the Statue of Liberty their green colour. Concept Tested: Green patina on copper – basic copper carbonate

NDA 2017-II

Q. 16. Zinc is used to protect iron from corrosion because zinc is

(a) more electropositive than iron

(b) cheaper than iron

(d) a good conductor of heat and electricity

Answer: (a) more electropositive than iron

Explanation: Zinc is more electropositive (higher in the reactivity/electrochemical series) than iron. This means zinc is oxidised preferentially – it acts as a sacrificial anode. Even if the zinc coating is scratched, zinc continues to protect iron by being oxidised first. Concept Tested: Galvanization – zinc more electropositive than iron

NDA 2017-I

Q. 17. Which one of the following elements is least reactive with water?

(a) Lithium

(b) Sodium

(d) Cesium

Answer: (a) Lithium

Explanation: Within Group 1 (alkali metals), reactivity increases down the group: Li < Na < K < Cs. Lithium is least reactive because it has the highest ionisation energy among Group 1 metals. Concept Tested: Reactivity of Group 1 metals – Li least reactive

Q. 18. Which one of the following elements corrodes rapidly?

(a) Aluminium

(b) Iron

(d) Silver

Answer: (b) Iron

Explanation: Iron corrodes (rusts) rapidly when exposed to moist air. Its oxide (rust) is porous and does not form a protective layer, so corrosion continues. Aluminium and zinc form protective oxide layers. Silver tarnishes (sulphide formation) but does not corrode rapidly. Concept Tested: Corrosion of metals – iron corrodes most rapidly

NDA 2016-I

Q. 19. Which one of the following elements will not react with dilute HCl to produce H₂ ?

(a) Hg

(b) Al

(d) Fe

Answer: (a) Hg

Explanation: Mercury (Hg) is below hydrogen in the reactivity series – it does not react with dilute HCl to produce H₂. Aluminium, magnesium and iron are all more reactive than hydrogen and will react with dilute HCl to produce H₂. Concept Tested: Reactivity series – metals below H do not produce H₂ with acids

NDA 2015-I

Q. 20. Thermal conductivity of aluminium, copper and stainless steel increases in the order

(a) Copper < Aluminium < Stainless Steel

(b) Stainless Steel < Aluminium < Copper

(d) Copper < Stainless Steel < Aluminium

Answer: (b) Stainless Steel < Aluminium < Copper

Explanation: Thermal conductivity (W/m·K approx.): Copper ≈ 400, Aluminium ≈ 200, Stainless steel ≈ 15–20. Increasing order: Stainless Steel < Aluminium < Copper. Concept Tested: Thermal conductivity order – stainless steel < aluminium < copper

NDA 2013-II

Q. 21. Statement I: Very little hydrogen is produced when sulphuric acid is added to calcium. Statement II: The salt that is produced, calcium sulphate, is insoluble.

(a) Both the statements are individually true and Statement II is the correct explanation of Statement I

(b) Both the statements are individually true but Statement II is not the correct explanation of Statement I

(d) Statement I is false but Statement II is true

Answer: (a) Both the statements are individually true and Statement II is the correct explanation of Statement I

Explanation: When H₂SO₄ reacts with Ca, CaSO₄ is formed. CaSO₄ is sparingly soluble – it forms an insoluble coating on the calcium surface, preventing further reaction. This is why very little H₂ is produced – the insoluble salt film blocks the acid from reaching the metal. Statement II directly explains Statement I. Concept Tested: Reaction of calcium with H₂SO₄ – insoluble CaSO₄ coating

Q. 22. Statement I: Zinc is used for galvanization to protect iron from rusting. Statement II: Zinc is more reactive towards oxygen than iron.

(a) Both the statements are individually true and Statement II is the correct explanation of Statement I

(b) Both the statements are individually true but Statement II is not the correct explanation of Statement I

(d) Statement I is false but Statement II is true

Answer: (a) Both the statements are individually true and Statement II is the correct explanation of Statement I

Explanation: Zinc is used to coat iron (galvanization). Zinc is more reactive than iron – it preferentially oxidises first and provides sacrificial protection. Even if the zinc coating is scratched, zinc still oxidises in preference to iron. Statement II correctly explains why zinc protects iron. Concept Tested: Galvanization – zinc as sacrificial anode protecting iron

★ JOVIK Exam Insight: Galvanization = coating iron with zinc. Zinc is more reactive than iron and acts as a sacrificial metal. This concept is tested frequently in NDA.

Q. 23. Oxygen on reaction with non-metals forms oxides, which are

(a) basic oxides

(b) acidic oxides

(d) neutral oxides

Answer: (b) acidic oxides

Explanation: Non-metals react with oxygen to form acidic oxides. For example: SO₂, SO₃, CO₂, NO₂, P₄O₁₀ – all are acidic oxides that dissolve in water to give acids. Metals form basic oxides. Some metals (Al, Zn) form amphoteric oxides. Concept Tested: Oxides of non-metals – acidic in nature

Q. 24. A gas is evolved when a piece of zinc metal placed in dilute sulphuric acid (H₂SO₄). What is the gas?

(a) Hydrogen

(b) Oxygen

(d) Sulphur dioxide

Answer: (a) Hydrogen

Explanation: Zn + H₂SO₄ → ZnSO₄ + H₂↑. Zinc reacts with dilute H₂SO₄ to produce zinc sulphate and hydrogen gas. This is a standard metal-acid reaction. Concept Tested: Zinc reacting with dilute H₂SO₄ – H₂ gas produced

Q. 25. Metalloids are

(a) alloys of alkali metals with other metals.

(b) colloids of metals.

(d) metals heavier than lead.

Answer: (c) elements having some properties of both metals and non-metals.

Explanation: Metalloids (semi-metals) are elements that have properties intermediate between metals and non-metals. Examples include silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and boron (B). They are used as semiconductors. Concept Tested: Metalloids – definition and examples

NDA 2011-I

Q. 26. Silver ware turns black after a period of time due to formation of :

(a) nitrate coating on silver.

(b) sulphide coating on silver.

(d) oxide coating on silver.

Answer: (b) sulphide coating on silver.

Explanation: Silver reacts with sulphur compounds (H₂S) in the air to form silver sulphide (Ag₂S), which is black. This is known as tarnishing. Silver chloride would be white, not black. Silver oxide is also brownish-black but tarnishing is primarily due to sulphide. Concept Tested: Tarnishing of silver – silver sulphide (Ag₂S)

NDA 2010-I

Q. 27. The best and the poorest conductors of heat are respectively

(a) silver (Ag) and lead (Pb)

(b) copper (Cu) and aluminium (Al)

(d) copper (Cu) and gold (Au)

Answer: (a) silver (Ag) and lead (Pb)

Explanation: Silver is the best conductor of heat (and also electricity) among metals. Lead is one of the poorest conductors of heat among common metals. The order of thermal conductivity: Ag > Cu > Au > Al > Pb (approximately). Concept Tested: Thermal conductivity of metals – silver best, lead poorest

★ JOVIK Exam Insight: Silver = best thermal conductor. Lead = poorest among common metals. NDA tests this fact frequently.

Q. 28. Which one among the following metals is more reactive than hydrogen?

(a) Mercury

(b) Copper

(d) Tin

Answer: (d) Tin

Explanation: In the electrochemical/reactivity series, metals above hydrogen can displace H₂ from dilute acids. Tin (Sn) is above hydrogen in the reactivity series, so it can react with dilute acids. Mercury, copper, and silver are all below hydrogen – they do not react with dilute acids. Concept Tested: Reactivity series – metals above hydrogen

Q. 29. Which one of the following is a transition metal?

(a) Aluminium (Al)

(b) Manganese (Mn)

(d) Calcium (Ca)

Answer: (b) Manganese (Mn)

Explanation: Transition metals are elements in d-block (Groups 3–12) of the periodic table. Manganese (Mn, Z=25) is a transition metal. Aluminium is in Group 13 (p-block). Magnesium (Group 2) and Calcium (Group 2) are alkaline earth metals. Concept Tested: Transition metals – identification of Manganese

Q. 30. Which one of the following elements will replace hydrogen from acids to form salts?

(a) Sulphur (S)

(b) Silicon (Si)

(d) Phosphorus (P)

Answer: (c) Zinc (Zn)

Explanation: Zinc is a metal that is more reactive than hydrogen in the activity series. It reacts with dilute acids: Zn + H₂SO₄ → ZnSO₄ + H₂. Sulphur, silicon and phosphorus are non-metals and do not replace hydrogen from acids in the same way. Concept Tested: Reactivity series – zinc displaces hydrogen from acids

Q. 31. Which one among the following is the correct order of reactivity of the elements?

(a) Cu > Mg > Zn > Na

(b) Na > Zn > Mg > Cu

(d) Na > Mg > Zn > Cu

Answer: (d) Na > Mg > Zn > Cu

Explanation: The correct reactivity order (most reactive first): Na > Mg > Zn > Cu. Sodium is the most reactive (Group 1). Magnesium is moderately reactive (Group 2). Zinc is less reactive. Copper is the least reactive among these four. Concept Tested: Reactivity series – order of Na, Mg, Zn, Cu

★ JOVIK Exam Insight: The standard NDA reactivity series sequence to remember: K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > H > Cu > Ag > Au.

NDA 2009-II

Q. 32. Aluminium is more reactive than iron but aluminium is less easily corroded than iron, because

(a) oxygen forms a protective oxide layer

(b) it is a noble metal

(d) iron forms ions

Answer: (a) oxygen forms a protective oxide layer

Explanation: Aluminium reacts with atmospheric oxygen to form a thin, hard layer of aluminium oxide (Al₂O₃) on its surface. This layer is impermeable and prevents further reaction – it is self-protective. Iron’s oxide (rust, Fe₂O₃·xH₂O) is porous and flaky and does not protect the metal underneath. Concept Tested: Passive layer on aluminium – protective Al₂O₃ coating

★ JOVIK Exam Insight: Aluminium is more reactive than iron in the reactivity series, yet corrodes less because its oxide layer is protective. This is a classic NDA distinction.