2 MARKs QUESTIONS
Q1. Why do ionic compounds have high melting and boiling points?
Approach: Think about strong electrostatic forces and their effect on energy requirement.
Answer:
- Ionic compounds contain strong electrostatic attraction between oppositely charged ions.
- A large amount of heat energy is required to break these bonds, causing high melting and boiling points.
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Q2. Why is aluminium used to make overhead power cables despite being reactive?
Approach: Consider conductivity, weight, and protective oxide layer.
Answer:
- Aluminium is lightweight, making cables easy to suspend.
- Forms a protective oxide layer preventing further corrosion.
- Has good electrical conductivity.
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Q3. How does copper react with steam and why?
Approach: Recall reactivity order and conditions of steam reaction.
Answer:
- Copper does not react with steam.
- It is less reactive and cannot displace hydrogen from water/steam.
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Q4. Why is sodium metal stored in kerosene?
Approach: Think explosive reaction with water/air.
Answer:
- Sodium reacts vigorously with oxygen and moisture, producing heat and possible fire.
- Kerosene prevents contact with air/water.
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Q5. Give two reasons why non-metals form covalent compounds.
Approach: Basis: electron affinity, inability to donate electrons.
Answer:
- They have high electronegativity and cannot lose electrons easily.
- They share electrons to achieve stable octet → covalent bonding.
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Q6. Why is graphite a good conductor of electricity but diamond is not?
Approach: Think about structure and free electrons.
Answer:
- Graphite has delocalised free electrons due to layered structure.
- Diamond has no free electrons; all are involved in tetrahedral bonding.
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Q7. Why do metals form basic oxides and non-metals form acidic oxides?
Approach: Link electron behaviour and pH.
Answer:
- Metal oxides react with water to give alkaline solutions (metal hydroxides).
- Non-metal oxides form acids when dissolved in water (e.g., CO₂ → H₂CO₃).
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Q8. Why does magnesium burn with a dazzling white flame?
Approach: Consider heat release and oxide formation.
Answer:
- Magnesium reacts vigorously with oxygen, releasing heat.
- Produces magnesium oxide, emitting bright white light.
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Q9. How does a more reactive metal displace a less reactive metal from its salt solution?
Approach: Use concept of reactivity series & electron transfer.
Answer:
- More reactive metal loses electrons easily and replaces less reactive metal ions.
- Example: Zn + CuSO₄ → ZnSO₄ + Cu.
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Q10. Why are alloys stronger than pure metals?
Approach: Think: irregular arrangement → restricted movement.
Answer:
- Alloying introduces atoms of different sizes, disturbing metal lattice.
- Reduces layer sliding, making alloys harder and stronger.
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Q11. Why do alkali metals like sodium and potassium react explosively with water, while magnesium reacts very slowly?
Answer:
- Sodium and potassium have very low ionisation energy, so they readily form M⁺ ions, releasing a high amount of heat.
- This heat ignites the hydrogen gas formed, causing explosive reaction.
- Magnesium forms Mg²⁺ slowly and produces insufficient heat for ignition.
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Q12. Explain why non-metals do not displace hydrogen from acids whereas metals do.
Answer:
- Metals are electropositive and can donate electrons, reducing H⁺ ions to hydrogen gas.
- Non-metals are electronegative and cannot lose electrons to reduce H⁺ ions, so no displacement occurs.
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Q13. Why does aluminium not corrode in the atmosphere even though it is a very reactive metal?
Answer:
- Aluminium reacts instantly with oxygen to form Al₂O₃.
- This oxide layer is thin, hard, and impermeable, preventing further corrosion.
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Q14. Silver and gold do not react with oxygen but tarnish in air. Explain.
Answer:
- They do not react with oxygen but react with sulphur compounds in air.
- They form Ag₂S coating → black tarnish.
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Q15. Why does graphite, a non-metal, conduct electricity while sulphur does not?
Answer:
- Graphite has delocalised electrons between layers.
- Sulphur consists only of covalently bonded S₈ molecules → no free electrons.
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3 MARKS QUESTIONS
Q1. Explain why metals are malleable and ductile while non-metals are brittle.
Approach: Talk about metallic bonding & layer sliding.
Answer:
- Metals have positive ions in a sea of delocalised electrons, allowing layers to slide.
- This makes metals malleable (hammered) and ductile (drawn).
- Non-metals have directional covalent bonds that break under force → brittle.
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Q2. Describe the extraction of aluminium from bauxite in three steps.
Approach: Mention ore → purification → electrolysis.
Answer:
- Purification (Bayer Process): Removes impurities like silica and iron oxide.
- Electrolysis of Alumina: Dissolved in molten cryolite to lower melting point.
- Formation of Aluminium: Aluminium is deposited at cathode; oxygen at anode.
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Q3. How does iron react with steam and with cold water? Explain with equations.
Approach: Compare reactivity conditions.
Answer:
- Cold water: No reaction due to low reactivity.
- Steam: Iron forms ferric oxide and hydrogen gas.
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Q4. Explain why noble metals like gold and platinum do not corrode.
Approach: Consider position in reactivity series.
Answer:
- They are very low in reactivity series.
- Do not react with oxygen, water, or atmospheric gases.
- Hence remain untarnished.
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Q5. Why does hydrogen gas evolve when acids react with metals but not when acids react with copper?
Approach: Connect hydrogen displacement rule.
Answer:
- Only metals more reactive than hydrogen can displace it.
- Copper is less reactive than hydrogen; no H₂ gas forms.
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Q6. Explain corrosion of iron and write two methods to prevent it.
Approach: Describe rusting conditions + solutions.
Answer:
- Rusting requires oxygen + moisture, forming hydrated iron oxide.
- Prevention:
- Galvanisation (coating with zinc).
- Painting or greasing to isolate metal from moisture.
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Q7. How does covalent bonding differ from ionic bonding? Give examples.
Approach: Define both + mention electron behaviour.
Answer:
- Ionic bond: Transfer of electrons (NaCl).
- Covalent bond: Sharing of electrons (H₂O, CO₂).
- Ionic → strong electrostatic forces; covalent → directional.
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Q8. Why do some metals like zinc and aluminium show both metallic and non-metallic properties?
Approach: Think amphoteric oxides & reactivity.
Answer:
- Their oxides (ZnO, Al₂O₃) are amphoteric, reacting with acids & bases.
- These metals can displace some metals yet still form covalent oxides.
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Q9. Explain how non-metals take part in displacement reactions with metals. Give an example.
Approach: Consider strong non-metal reactivity like halogens.
Answer:
- Highly reactive non-metals (Cl₂) can displace less reactive halogens or metals.
- Example: Cl₂ + 2NaBr → 2NaCl + Br₂.
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Q10. Describe the properties and uses of sodium chloride.
Approach: Chemical, physical, and industrial uses.
Answer:
- White crystalline ionic compound.
- Highly soluble in water.
- Used in food, chlorine production, and sodium hydroxide manufacture.
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5 MARKS QUESTIONS
Q1. Explain the physical and chemical properties of metals and non-metals with at least 5 examples each.
Approach: List properties separately; ensure clear comparison.
Answer:
Physical Properties of Metals:
- Malleability – beaten into sheets (Al foil).
- Ductility – drawn into wires (Cu wires).
- Conductivity – good heat/electric conductors (Ag, Cu).
- Lustrous – shiny appearance (Au jewellery).
- High melting points – Fe, W.
Physical Properties of Non-Metals:
- Brittle (S, P).
- Poor conductors (Sulphur).
- Low density (gases like N₂).
- Non-lustrous usually.
- Low melting/boiling points (except C).
Chemical Properties of Metals:
- React with oxygen → metal oxides.
- React with acids → H₂ gas.
- Displacement reactions.
- Form ionic compounds.
- React with water (Na, K).
Chemical Properties of Non-Metals:
- Form acidic oxides.
- Poorly react with acids.
- React with hydrogen → covalent hydrides.
- React with metals → ionic compounds.
- Do not displace hydrogen.
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Q2. Describe the steps of electrolytic refining of copper and explain the reactions at both electrodes.
Approach: Define refining → explain setup → reactions.
Answer:
- Purpose: To obtain pure copper from impure samples.
- Setup:
- Anode: Impure copper
- Cathode: Pure copper plate
- Electrolyte: Copper sulphate solution
Process:
- Electric current passes → anode dissolves.
- Cu²⁺ ions migrate to cathode → deposit as pure Cu.
Reactions:
- Anode: Cu(s) → Cu²⁺ + 2e⁻
- Cathode: Cu²⁺ + 2e⁻ → Cu(s)
Result:
Pure copper accumulates at cathode; impurities fall as anode mud.
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Q3. Explain the formation, properties, and uses of ionic compounds in detail.
Approach: Define → structure → physical/chemical → examples.
Answer:
Formation:
- Transfer of electrons between metal & non-metal.
- Na gives 1e⁻ to Cl → Na⁺ Cl⁻.
Properties:
- High melting/boiling points.
- Soluble in water.
- Conduct electricity in molten/aqueous state.
- Hard & brittle.
- Form crystalline solids.
Uses:
- NaCl in food, chemicals.
- CaO in cement.
- NaOH in soap industry.
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Q4. Explain the reactivity series and its importance in displacement reactions and metal extraction.
Approach: Define series → its use in reactions → extraction.
Answer:
Reactivity Series: Arrangement of metals in decreasing activity.
Importance:
- Predicts displacement reactions.
- High reactive metals extracted by electrolysis (Na, Ca).
- Moderately reactive metals extracted via reduction with carbon (Fe).
- Low reactive metals obtained by heat alone (Ag, Au).
- Determines choice of reducing agent.
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Q5. Give a detailed explanation of corrosion, conditions required, its consequences, and three prevention methods.
Approach: Definition → reaction → effects → prevention.
Answer:
Corrosion: Slow deterioration of a metal by chemical reaction with surroundings (rusting).
Conditions:
- Moisture + oxygen
- Presence of salts
Consequences:
- Weakens structures.
- Loss of money.
- Degrades metal properties.
Prevention:
- Galvanisation
- Electroplating
- Painting or greasing
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Q6. Explain amphoteric oxides with examples, reactions, and importance.
Approach: Define → reactions with acid + base → examples.
Answer:
- Amphoteric oxides react with both acids and bases.
Examples: Al₂O₃, ZnO
Reactions:
- With Acid: Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
- With Base: Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O
Importance:
- Used in extraction, refining, and neutralisation processes.
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Q7. Describe the reactions of metals with oxygen, water, and acids with at least 2 examples each.
Approach: Give reaction + example + conditions.
Answer:
With Oxygen:
- 2Mg + O₂ → 2MgO
- 4Al + 3O₂ → 2Al₂O₃
With Water:
- 2Na + 2H₂O → 2NaOH + H₂
- Fe + H₂O (steam) → Fe₃O₄ + H₂
With Acids:
- Zn + 2HCl → ZnCl₂ + H₂
- Mg + 2H₂SO₄ → MgSO₄ + H₂
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Q8. Explain the process of alloy formation and describe how alloying changes metal properties. Give 4 examples.
Approach: Define alloying → how properties change → examples.
Answer:
- Alloying mixes metals/non-metals to improve properties.
Changes:
- Increased hardness
- Resistance to corrosion
- Better tensile strength
- Lower melting point sometimes
Examples:
- Brass (Cu + Zn)
- Bronze (Cu + Sn)
- Stainless steel (Fe + C + Cr + Ni)
- Solder (Pb + Sn)
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