Metals and Non Metals – Textbook Exercise Questions
1. Which of the following pairs will give displacement reactions?
(d) AgNO₃ solution and copper metal.
A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its salt solution.[1] According to the reactivity series, copper is more reactive than silver, so it will displace silver from silver nitrate (AgNO₃) solution. In the other options, the metals are less reactive than the metals in the salt solutions, so no reaction will occur.
2. Which of the following methods is suitable for preventing an iron frying pan from rusting?
(c) applying a coating of zinc.
Applying a coating of zinc, a process known as galvanization, is a suitable method for preventing an iron frying pan from rusting. Zinc is more reactive than iron and will corrode first, protecting the iron. While applying grease or paint can also prevent rust, they are not ideal for a frying pan as grease would be removed during washing and paint could chip off and contaminate food.
3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be:
(a) calcium.
Calcium reacts with oxygen to form calcium oxide (CaO), which is an ionic compound with a high melting point. Calcium oxide is also soluble in water, forming calcium hydroxide. The other options are less likely: carbon and silicon form oxides that are not readily soluble in water, and iron forms oxides that are largely insoluble.
4. Food cans are coated with tin and not with zinc because:
(c) zinc is more reactive than tin.
Zinc is more reactive than tin. If zinc were used to coat food cans, it would be more likely to react with the acids present in food, which could contaminate the food and make it unsafe to eat. Tin is less reactive and therefore provides a safer protective coating.
5. You are given a hammer, a battery, a bulb, wires and a switch.
(i) How could you use them to distinguish between samples of metals and non-metals?
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Malleability Test (using the hammer): Metals are generally malleable, meaning they can be hammered into thin sheets without breaking. Non-metals are typically brittle and will break or shatter if hammered. You can strike each sample with the hammer to observe this property.
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Conductivity Test (using the battery, bulb, wires, and switch): Metals are good conductors of electricity. You can create a simple circuit with the battery, bulb, wires, and switch. By placing the sample into the circuit, you can test its conductivity. If the bulb lights up, the sample is a metal. If it does not, it is a non-metal.
(ii) Assess the usefulness of these tests in distinguishing between metals and non-metals.
These tests are very useful for distinguishing between most metals and non-metals as they test for two key characteristic properties. However, there are exceptions. For example, some metalloids may exhibit properties of both metals and non-metals. Also, some non-metals like graphite (a form of carbon) can conduct electricity. Therefore, while these tests are generally reliable, they may not be conclusive for all elements.
6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Amphoteric oxides are metal oxides that can react with both acids and bases to produce salt and water. Examples of amphoteric oxides include aluminum oxide (Al₂O₃) and zinc oxide (ZnO).
7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Metals that are more reactive than hydrogen in the reactivity series will displace hydrogen from dilute acids.
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Metals that will displace hydrogen: Zinc (Zn) and Iron (Fe).
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Metals that will not displace hydrogen: Copper (Cu) and Silver (Ag).
8. In the electrolytic refining a metal M, what would you take as the anode, the cathode and the electrolyte?
In the electrolytic refining of a metal M:
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Anode: The impure block of metal M.
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Cathode: A thin strip of pure metal M.
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Electrolyte: A salt solution of the metal M (e.g., a solution of MSO₄).
9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown in figure.
(a) What will be the action of gas on
(i) dry litmus paper?
There will be no change in the color of the dry litmus paper.
(ii) moist litmus paper?
The gas produced is sulfur dioxide (SO₂), which is an acidic oxide. When it comes in contact with moist litmus paper, it will turn the blue litmus paper red.
(b) Write a balanced chemical equation for the reaction taking place.
S(s) + O₂(g) → SO₂(g)
10. State two ways to prevent the rusting of iron.
Two common ways to prevent the rusting of iron are:
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Painting or Oiling: Applying a coat of paint or oil creates a barrier that prevents the iron from coming into contact with air and moisture.
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Galvanization: Coating the iron with a layer of a more reactive metal, such as zinc. The zinc corrodes first, protecting the iron underneath.
11. What type of oxides are formed when non-metals combine with oxygen?
Non-metals generally combine with oxygen to form acidic oxides. These oxides react with water to form acids. For example, sulfur dioxide (SO₂) reacts with water to form sulfurous acid (H₂SO₃).
12. Give reasons:
(a) Platinum, gold and silver are used to make jewellery.
Platinum, gold, and silver are used to make jewelry because they are very unreactive and do not corrode or tarnish easily. They are also lustrous (shiny) and malleable, which makes them easy to shape into intricate designs.
(b) Sodium, potassium and lithium are stored under oil.
Sodium, potassium, and lithium are highly reactive metals that react vigorously with air and water. They are stored under oil to prevent them from coming into contact with oxygen and moisture in the atmosphere, which could cause them to catch fire.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
Although aluminum is a reactive metal, it forms a thin, tough, and non-reactive layer of aluminum oxide on its surface when exposed to air. This protective layer prevents the aluminum from reacting further with food and water, making it safe for use in cooking utensils.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
It is easier to extract a metal from its oxide than from its carbonate or sulfide ore. Therefore, carbonate and sulfide ores are converted into oxides through processes like calcination (for carbonates) and roasting (for sulfides) before the metal is extracted, usually by reduction.
13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Copper vessels tarnish due to the formation of a layer of basic copper carbonate on their surface. Lemon and tamarind juice contain acids (citric acid and tartaric acid, respectively). These acids react with the basic copper carbonate and dissolve the layer, restoring the shiny surface of the copper.
14. Differentiate between metals and non-metals.
| Property | Metals | Non-metals |
| Lustre | Have a shiny appearance. | Have a dull appearance. |
| Hardness | Generally hard (except for sodium, potassium, etc.). | Generally soft (except for diamond). |
| State | Solid at room temperature (except mercury). | Exist as solids, liquids, or gases. |
| Malleability | Can be beaten into thin sheets. | Brittle, break when hammered. |
| Ductility | Can be drawn into wires. | Not ductile. |
| Conductivity | Good conductors of heat and electricity. | Poor conductors of heat and electricity (except graphite). |
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Differentiate between metals and non-metals on the basis of their chemical properties.
| Property | Metals | Non-metals |
| Oxides | Form basic or amphoteric oxides. | Form acidic or neutral oxides. |
| Reaction with Acids | Generally react with dilute acids to produce hydrogen gas. | Do not generally react with dilute acids. |
| Reaction with Water | Some react with water to form hydroxides and hydrogen gas. | Do not generally react with water. |
| Ion Formation | Tend to lose electrons to form positive ions (cations). | Tend to gain or share electrons to form negative ions (anions) or covalent bonds. |
| Reducing/Oxidizing Agent | Are good reducing agents. | Are good oxidizing agents. |
15. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?
The solution the man used was likely Aqua Regia. Aqua Regia is a highly corrosive mixture of concentrated nitric acid and concentrated hydrochloric acid. It is one of the few substances that can dissolve noble metals like gold. By dipping the gold bangles in this solution, the man dissolved the outer layer of the gold, which removed the dullness and made them sparkle. However, this process also removed a significant amount of gold, causing the weight of the bangles to be drastically reduced.
16. Give the reasons why copper is used to make hot water tanks but steel (an alloy of iron) is not.
Copper is used for hot water tanks for the following reasons:
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Good Conductor of Heat: Copper is an excellent conductor of heat, which allows for efficient transfer of heat to the water.
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Corrosion Resistance: Copper is a less reactive metal and is resistant to corrosion from water, ensuring a longer lifespan for the tank.
In contrast, steel, which is an alloy of iron, is more reactive and prone to rusting, especially in hot water. This would lead to the deterioration of the tank and contamination of the water.
InText Questions
1. Give an example of a metal which:
(i) is a liquid at room temperature
Mercury (Hg)
(ii) can be easily cut with a knife
Sodium (Na) or Potassium (K)
(iii) is the best conductor of heat
Silver (Ag)
(iv) is a poor conductor of heat.
Lead (Pb) or Mercury (Hg)
2. Explain the meaning of malleable and ductile.
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Malleable: Malleability is the property of a substance that allows it to be hammered or pressed into thin sheets without breaking. Metals are generally malleable.
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Ductile: Ductility is the property of a substance that allows it to be drawn into thin wires.Metals are typically ductile.
3. Why is sodium kept immersed in kerosene oil?
Sodium is a very reactive metal that reacts vigorously with both the oxygen and moisture present in the air. To prevent this reaction, which can cause it to catch fire, sodium is stored under kerosene oil, which acts as a protective barrier.
4. Write equation for the reactions of
(i) iron with steam
3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)
(ii) calcium and potassium with water.
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Calcium with water: Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)
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Potassium with water: 2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g)
5. Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows:
(Assuming a standard reactivity series where reactivity decreases down a group)
(i) Which is the most reactive metal?
Based on typical displacement reactions, the metal that displaces others from their salt solutions is the most reactive. Without the actual table, a general principle is that a more reactive metal will displace a less reactive one. For example, if Metal A displaces Metal B from its salt solution, A is more reactive than B.
(ii) What would you observe if B is added to a solution of copper (II) sulphate?
To answer this, we need to know the relative reactivity of metal B and copper. If B is more reactive than copper, it will displace copper from the copper (II) sulfate solution. You would observe the blue color of the copper sulfate solution fading and a reddish-brown deposit of copper metal forming on the surface of metal B. If B is less reactive than copper, no reaction would occur.
(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
To arrange the metals in order of decreasing reactivity, you would need to analyze the results of the displacement reactions. The metal that displaces the most other metals is the most reactive, and the one that is displaced by all others is the least reactive.
6. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H₂SO₄.
Hydrogen gas is produced when a reactive metal reacts with dilute hydrochloric acid.
The chemical reaction when iron reacts with dilute sulfuric acid (H₂SO₄) is:
Fe(s) + H₂SO₄(aq) → FeSO₄(aq) + H₂(g)
7. What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.
Zinc is more reactive than iron. Therefore, when zinc is added to a solution of iron (II) sulfate, it will displace the iron. You would observe the pale green color of the iron (II) sulfate solution gradually fading, and a grayish deposit of iron metal forming on the zinc strip.
The chemical reaction is:
Zn(s) + FeSO₄(aq) → ZnSO₄(aq) + Fe(s)
8. (i) Write the electron-dot structures for sodium, oxygen and magnesium.
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Sodium (Na): Na has one valence electron. Its electron-dot structure is Na•
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Oxygen (O): O has six valence electrons. Its electron-dot structure is :Ö:
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Magnesium (Mg): Mg has two valence electrons. Its electron-dot structure is •Mg•
(ii) Show the formation of Na₂O and MgO by the transfer of electrons.
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Formation of Na₂O: Two sodium atoms each lose one electron to form Na⁺ ions. One oxygen atom gains these two electrons to form an O²⁻ ion.
2Na• + :Ö: → 2Na⁺ + [:Ö:]²⁻ → Na₂O -
Formation of MgO: One magnesium atom loses two electrons to form an Mg²⁺ ion. One oxygen atom gains these two electrons to form an O²⁻ ion.
•Mg• + :Ö: → Mg²⁺ + [:Ö:]²⁻ → MgO
(iii) What are the ions present in the above compounds?
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In Na₂O, the ions present are sodium ions (Na⁺) and oxide ions (O²⁻).
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In MgO, the ions present are magnesium ions (Mg²⁺) and oxide ions (O²⁻).
9. Why do ionic compounds have high melting points?
Ionic compounds have high melting points because they are made up of positively and negatively charged ions that are held together by strong electrostatic forces of attraction. A large amount of energy is required to overcome these strong forces and break the bonds, resulting in high melting points.
10. Define the terms:
(a) mineral: A mineral is a naturally occurring, inorganic solid with a definite chemical composition and a crystalline structure.
(b) ore: An ore is a type of rock that contains sufficient minerals with important elements including metals that can be economically extracted from the rock.
(c) gangue: Gangue is the commercially worthless material that surrounds, or is closely mixed with, a wanted mineral in an ore deposit.
11. Name two metals which are found in nature in the free state.
Two metals that are found in their free or native state in nature are gold (Au) and platinum (Pt). This is because they are very unreactive.
12. What chemical process is used for obtaining a metal from its oxide?
The chemical process used to obtain a metal from its oxide is reduction. This involves removing oxygen from the metal oxide. A common method is heating the metal oxide with a reducing agent such as carbon (coke) or a more reactive metal.
13. Metallic oxides of zinc, magnesium and copper were heated with the following metals:
To determine where displacement reactions will occur, we need to compare the reactivity of the metals. A more reactive metal will displace a less reactive metal from its oxide. The reactivity order is generally Magnesium > Zinc > Copper.
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Zinc Oxide (ZnO):
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With Magnesium: Displacement will occur (Mg + ZnO → MgO + Zn).
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With Copper: No reaction.
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Magnesium Oxide (MgO):
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With Zinc: No reaction.
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With Copper: No reaction.
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Copper Oxide (CuO):
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With Zinc: Displacement will occur (Zn + CuO → ZnO + Cu).
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With Magnesium: Displacement will occur (Mg + CuO → MgO + Cu).
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14. Which metals do not corrode easily?
Metals that do not corrode easily are the ones that are less reactive, such as gold, platinum, and silver.
15. What are alloys?
An alloy is a mixture of two or more elements, where at least one element is a metal. Alloys are created to enhance the properties of the constituent metals, such as making them harder, stronger, or more resistant to corrosion. Examples include brass (an alloy of copper and zinc) and steel (an alloy of iron and carbon).
