Home · Schooling · CBSE · Class 10 · Science · Metals and Non-metals · End-of-chapter exercises

NCERT Class 10 Science Metals and Non-metals: Exercise Solutions

Step-by-step working for every question of End-of-chapter exercises in NCERT's Class 10 Science book, chapter “Metals and Non-metals”, written by Shishya. Each question is in our own short words; open the NCERT chapter for the exact wording and figures.

1. Exercises Q1

   Which pair gives a displacement reaction: (a) NaCl solution and copper (b) MgCl₂ solution and aluminium (c) FeSO₄ solution and silver (d) AgNO₃ solution and copper?

   1. A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its salt solution.
      why?

      A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

   2. We must compare the reactivity of the metal with the metal present in the solution using the reactivity series.
   3. In option (a), copper is less reactive than sodium, so it cannot displace sodium from NaCl solution.
      why?

      A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

   4. In option (b), aluminium is less reactive than magnesium, so it cannot displace magnesium from MgCl₂ solution.
      why?

      A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

   5. In option (c), silver is less reactive than iron, so it cannot displace iron from FeSO₄ solution.
      why?

      A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

   6. In option (d), copper is more reactive than silver, so it can displace silver from AgNO₃ solution.
      why?

      A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

   7. The reaction is Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag, which is a valid displacement reaction.

   Answer: (d) AgNO₃ solution and copper

   Report an error in this solution

2. Exercises Q2

   Which suits preventing an iron frying pan from rusting: (a) grease (b) paint (c) a coating of zinc (d) all of these?

   1. Rusting needs both air (oxygen) and water, so the iron surface must be covered.
   2. Grease and paint do keep out air and water, but a frying pan is heated strongly and touches food: grease burns off and paint would burn, peel and get into the food.
   3. A coating of zinc (galvanisation) stays on when the pan is heated and keeps protecting the iron even if it is scratched, because zinc is more reactive and corrodes first.
   4. So the suitable method for a frying pan is a zinc coating.

   Answer: (c) Applying a coating of zinc

   Report an error in this solution

3. Exercises Q3

   An element forms an oxide with a high melting point that dissolves in water. The element is likely to be (a) calcium (b) carbon (c) silicon (d) iron.

   1. The oxide of the element has a high melting point, which is a characteristic property of ionic compounds.
   2. Ionic oxides are typically formed by metals reacting with oxygen.
   3. Among the given options, carbon, silicon, and iron do not form oxides that are both high-melting and soluble in water in the same way.
   4. Calcium is a metal that forms calcium oxide (CaO), which has a high melting point and dissolves in water to form calcium hydroxide.
   5. Therefore, the element is likely to be calcium.

   Answer: (a) calcium

   Report an error in this solution

4. Exercises Q4

   Food cans are coated with tin, not zinc, because zinc is (a) costlier (b) higher-melting (c) more reactive (d) less reactive than tin.

   1. Zinc is more reactive than tin in the reactivity series of metals.
   2. A more reactive metal reacts with the food inside the can, which can spoil the food or make it unsafe to eat.
   3. Tin is less reactive than zinc, so it does not react with the food and keeps it safe.
   4. Therefore, food cans are coated with tin instead of zinc to prevent chemical reactions with the food.

   Answer: (c) zinc is more reactive than tin

   Report an error in this solution

5. Exercises Q5

   With a hammer, a battery, a bulb, wires and a switch: (a) how can you tell metals from non-metals? (b) How useful are these tests?

   1. (a) Take a piece of the substance and hit it with a hammer; if it flattens into a thin sheet without breaking, it is a metal because it is malleable.
   2. (a) Connect the substance to a battery, bulb, and wires using a switch; if the bulb glows when the switch is on, the substance is a metal because it conducts electricity.
   3. (b) These tests are useful for identifying metals and non-metals in a simple laboratory or classroom setting.
   4. (b) The tests are useful but not perfect: graphite is a non-metal that conducts electricity, and some metals (such as sodium and potassium) are too soft for the hammer test to be telling; mercury is a liquid. So the results should be read together with other properties.

   Answer: (a) Hammer test: metals are malleable (flatten into sheets), non-metals break or powder. Circuit test: metals conduct electricity so the bulb glows, non-metals usually do not. (b) Useful for most samples, but there are exceptions such as graphite (a non-metal that conducts).

   Report an error in this solution

6. Exercises Q6

   What are amphoteric oxides? Give two examples.

   1. Amphoteric oxides are metal oxides that can react with both acids and bases to form salt and water.
   2. These oxides show both acidic and basic properties depending on the reagent they react with.
   3. Aluminium oxide (Al₂O₃) is an example that reacts with hydrochloric acid to form aluminium chloride and water.
   4. Aluminium oxide also reacts with sodium hydroxide to form sodium aluminate and water.
   5. Zinc oxide (ZnO) is another example that reacts with acids to form zinc salts and with bases to form zincates.

   Answer: Amphoteric oxides react with both acids and bases; examples are Al₂O₃ and ZnO.

   Report an error in this solution

7. Exercises Q7

   Name two metals that displace hydrogen from dilute acids and two that do not.

   1. Metals above hydrogen in the reactivity series displace hydrogen from dilute acids.
      why?

      A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

   2. Metals below hydrogen in the reactivity series do not displace hydrogen from dilute acids.
      why?

      A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

   3. Two metals that displace hydrogen are zinc and iron.
      why?

      A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

   4. Two metals that do not displace hydrogen are copper and silver.
      why?

      A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

   Answer: Metals that displace hydrogen: zinc, iron; Metals that do not displace hydrogen: copper, silver

   Report an error in this solution

8. Exercises Q8

   In electrolytic refining of a metal M, what are the anode, the cathode and the electrolyte?

   1. In electrolytic refining, the impure metal M is placed as the anode.
   2. The pure metal M is placed as the cathode.
   3. The electrolyte is an aqueous solution of a salt of the metal M.
   4. When current flows, metal ions from the anode dissolve into the electrolyte.
   5. These ions move to the cathode and get deposited as pure metal.
   6. Impurities settle at the bottom of the cell as anode mud.

   Answer: Anode: impure metal M; Cathode: pure metal M; Electrolyte: aqueous solution of a salt of metal M

   Report an error in this solution

9. Exercises Q9

   Pratyush heats sulphur powder and collects the gas in an inverted test tube. (a) What does the gas do to (i) dry litmus paper (ii) moist litmus paper? (b) Write the balanced equation.

   Uses a figure printed in the NCERT book — open the chapter above to see it.

   1. Sulphur burns in air to produce sulphur dioxide gas.
   2. Sulphur dioxide is an acidic gas.
   3. Acidic gases do not change the colour of dry litmus paper.
   4. Sulphur dioxide turns moist blue litmus paper red.
   5. The balanced chemical equation for the reaction is S + O2 → SO2.
      why?

      A balanced equation has the same number of atoms of each element on both sides, because atoms are neither created nor destroyed in a chemical reaction (law of conservation of mass). Only the numbers in front (coefficients) change, never the formulas.

   Answer: (a)(i) No change; (ii) Turns blue litmus red; (b) S + O2 → SO2

   Report an error in this solution

10. Exercises Q10

    State two ways to prevent rusting of iron.

    1. Rusting occurs when iron reacts with oxygen and moisture in the air.
    2. One way to prevent rusting is to apply a layer of paint or oil on the iron surface.
    3. This coating acts as a barrier that stops oxygen and water from reaching the iron.
    4. Another way to prevent rusting is to make an alloy of iron with other metals.
    5. Stainless steel is an example of such an alloy which does not rust easily.

    Answer: Two ways to prevent rusting are: (1) Applying paint or oil to the iron surface, and (2) Making an alloy like stainless steel.

    Report an error in this solution

11. Exercises Q11

    What type of oxides do non-metals form with oxygen?

    1. Non-metals react with oxygen to form oxides.
    2. These oxides are generally acidic in nature.
    3. When dissolved in water, they form acids.
    4. For example, carbon burns in oxygen to form carbon dioxide, which is an acidic oxide.
    5. Sulphur burns in oxygen to form sulphur dioxide, which is also an acidic oxide.

    Answer: Non-metals form acidic oxides with oxygen.

    Report an error in this solution

12. Exercises Q12

    Give reasons: (a) platinum, gold and silver are used for jewellery (b) sodium, potassium and lithium are stored under oil (c) aluminium is very reactive yet used for cooking utensils (d) carbonate and sulphide ores are converted to oxides during extraction.

    1. (a) Platinum, gold and silver are used for jewellery because they are lustrous, malleable, and do not react easily with air or moisture.
    2. (b) Sodium, potassium and lithium are stored under oil because they are highly reactive and react violently with moisture or oxygen in the air.
    3. (c) Aluminium is used for cooking utensils despite being reactive because a thin, tough layer of aluminium oxide forms on its surface, which prevents further reaction.
    4. (d) Carbonate and sulphide ores are converted to oxides because oxides are easier to reduce to the free metal during the extraction process.

    Answer: (a) Lustrous and unreactive; (b) Highly reactive with air/moisture; (c) Protective oxide layer forms; (d) Oxides are easier to reduce.

    Report an error in this solution

13. Exercises Q13

    Why do lemon or tamarind juice clean tarnished copper vessels?

    1. Copper vessels tarnish because they react with moisture and air to form a green layer of basic copper carbonate, Cu₂(OH)₂CO₃.
    2. Lemon and tamarind juice contain weak organic acids such as citric acid and tartaric acid.
    3. These acids react with the basic copper carbonate layer on the surface of the vessel.
    4. The chemical reaction produces soluble copper salts, water, and carbon dioxide gas.
    5. Since the tarnish layer is converted into soluble salts, it is washed away, making the copper surface look shiny and clean.

    Answer: Lemon and tamarind juice contain acids that react with the basic copper carbonate tarnish layer to form soluble salts, thereby cleaning the vessel.

    Report an error in this solution

14. Exercises Q14

    Differentiate metals and non-metals by their chemical properties.

    1. Metals react with oxygen to form basic oxides, whereas non-metals form acidic or neutral oxides.
    2. Metals react with dilute acids to release hydrogen gas, but non-metals do not react with acids.
    3. Metals can displace less reactive metals from their salt solutions, while non-metals do not show this displacement property.
       why?

       A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.

    4. Metals react with water to form hydroxides and release hydrogen, whereas non-metals generally do not react with water.

    Answer: Metals form basic oxides, react with acids to release hydrogen, and displace less reactive metals; non-metals form acidic oxides, do not react with acids, and do not displace metals.

    Report an error in this solution

15. Exercises Q15

    A fake goldsmith dipped gold bangles in a solution; they sparkled but lost much weight. What solution did he use?

    1. Gold does not react with ordinary acids, so the solution must have been one that dissolves gold.
    2. Aqua regia, a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3 : 1, can dissolve gold.
    3. When the bangles were dipped in it, the outer layer of gold dissolved, which exposed a fresh shiny surface.
    4. The dissolved gold stayed in the solution, so the bangles lost weight while looking new.

    Answer: He used aqua regia (concentrated HCl and concentrated HNO₃ in the ratio 3 : 1), which dissolved the outer layer of gold.

    Report an error in this solution

16. Exercises Q16

    Why is copper, not steel, used for hot water tanks?

    1. Copper is a good conductor of heat, so it transfers heat to the water quickly and evenly.
    2. Steel is an alloy of iron and carbon, and iron reacts with steam at high temperatures.
    3. When iron reacts with steam, it forms iron oxide, which causes the tank to rust and weaken.
    4. Copper does not react with steam or hot water, so it remains durable over time.
    5. Therefore, copper is preferred for hot water tanks to ensure longevity and efficient heating.

    Answer: Copper is used instead of steel because it conducts heat well and does not react with steam or hot water, whereas steel (iron) reacts with steam to form rust, weakening the tank.

    Report an error in this solution

← Metals and Non-metals: notes, practice and all exercises