NCERT Solutions for Class 10 Chemistry Chapter 3 : Metals and Non metals

Q: Q1. How are metals extracted from their ores?

Answer: Ores are polluted with a variety of impurities known as gangue. The extraction techniques are determined by the differences in physical and chemical qualities between the gangue and the ores. Different metals have different levels of reactivity. The extraction processes are based on this. Heating alone can purify metals that are less reactive. Roasting and calcination are used to refine medium reactive metals. Electrolytic reduction refines extremely reactive metals.

Q: Q2. Why do silver objects become black after a while when exposed to air?

Answer: They become tarnished when they react with atmospheric air, forming silver sulphide.

Question 1

Gives an example of a metal which:

a)liquid at room temperature

b)can be cut with a knife

c)is the best conductor of heat

d)is a poor conductor of heat

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Answer

(A)A metal which is a liquid at room temperature - Mercury

(H g)

Mercury is liquid at room temperature.

(B)A metal which can be cut with a knife - Sodium

(N a)

Lithium, sodium and potassium are all soft metals that are easily cut with a scalpel or knife.

(C)A metal which is the best conductor of heat - Silver

(A g)

Silver is the best conductor of both heat and electricity among metals.

(D) A metal which is a poor conductor of heat - Bismuth

(B i)

Bismuth is the poor conductor of heat due to less number of free electrons

Answer

(A)A metal which is a liquid at room temperature - Mercury

(H g)

Mercury is liquid at room temperature.

(B)A metal which can be cut with a knife - Sodium

(N a)

Lithium, sodium and potassium are all soft metals that are easily cut with a scalpel or knife.

(C)A metal which is the best conductor of heat - Silver

(A g)

Silver is the best conductor of both heat and electricity among metals.

(D) A metal which is a poor conductor of heat - Bismuth

(B i)

Bismuth is the poor conductor of heat due to less number of free electrons

Question 2

Explain the meanings of malleability and ductility.

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Answer

Malleability: Some metals can be beaten into thin sheets. This property is called Malleability.
Ductility: The ability of metals to be drawn into thin wires is called ductility.

Answer

Malleability: Some metals can be beaten into thin sheets. This property is called Malleability.
Ductility: The ability of metals to be drawn into thin wires is called ductility.

Question 3

An element reacts with oxygen to give a compound which is basic in nature. This compound is also soluble in water. The element is likely to be:

A

Sodium

B

Carbon

C

Bromine

D

Iron

Medium

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Answer

Metal oxides are basic in nature. Hence, answer could be options

A

and

D

. But most metal oxides are insoluble in water and only some of these dissolve in water to form alkalis. Sodium oxide and potassium oxide dissolve in water to produce alkalis as follows –

N a_{2} O (s) + H_{2} O (l) \to 2 N a O H (a q)

So, the correct option is

A

Answer

Metal oxides are basic in nature. Hence, answer could be options

A

and

D

. But most metal oxides are insoluble in water and only some of these dissolve in water to form alkalis. Sodium oxide and potassium oxide dissolve in water to produce alkalis as follows –

N a_{2} O (s) + H_{2} O (l) \to 2 N a O H (a q)

So, the correct option is

A

Question 4

You are given a hammer, a battery, a bulb, wires and a switch.

(a) How could you use them to distinguish between samples of metals and non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

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Answer

(a) If the substance can be hammered to convert into sheets then it is metal if it is broken into pieces then it is non-metal.

(b) Set up the circuit arrangement using bulb, battery, wire and switch. Place the object between the ends of circuit. If the bulb starts glowing then the substance is a metal otherwise it is non-metal because metals are good conductor of electricity.

Generally above methods can be used to identify metals and non-metals. But there are some exceptions also for example sodium is metal which is not malleable in fact it is brittle. Graphite, allotrope of non-metal carbon, is a good conductor of electricity.

Answer

(a) If the substance can be hammered to convert into sheets then it is metal if it is broken into pieces then it is non-metal.

(b) Set up the circuit arrangement using bulb, battery, wire and switch. Place the object between the ends of circuit. If the bulb starts glowing then the substance is a metal otherwise it is non-metal because metals are good conductor of electricity.

Generally above methods can be used to identify metals and non-metals. But there are some exceptions also for example sodium is metal which is not malleable in fact it is brittle. Graphite, allotrope of non-metal carbon, is a good conductor of electricity.

Question 5

What are amphoteric oxides? Give two examples of amphoteric oxides.

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Answer

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Question 6

Name two metals which will displace hydrogen from dilute acids and two metals which will not.

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Answer

Metals that are more reactive than hydrogen displace it from dilute acids.

For example: sodium and potassium.

Metals that are less reactive than hydrogen do not displace it.

For example: copper and silver.

Answer

Metals that are more reactive than hydrogen displace it from dilute acids.

For example: sodium and potassium.

Metals that are less reactive than hydrogen do not displace it.

For example: copper and silver.

Question 7

In the electrolytic refining of a metal

M

, what would you take as the anode, the cathode, and the electrolyte?

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Answer

A rod of impure metal

M

would be used as an anode and a thin strip of pure metal

M

would be used as the cathode. A water-soluble salt of metal

M

would be used as an electrolyte. When current is passed through the electrolyte, the impure metal from the anode is dissolved in the electrolyte and an equal amount of pure metal from the electrolyte is deposited on the cathode.

Answer

A rod of impure metal

M

would be used as an anode and a thin strip of pure metal

M

would be used as the cathode. A water-soluble salt of metal

M

would be used as an electrolyte. When current is passed through the electrolyte, the impure metal from the anode is dissolved in the electrolyte and an equal amount of pure metal from the electrolyte is deposited on the cathode.

Question 8

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 the figure above.

(a) What will be the action of gas on
(i) dry litmus paper?
(ii) moist litmus paper?
(b) Write a balanced chemical equation for the reaction taking place.

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Answer

When sulphur is heated in air it produce sulphur dioxide

S O_{2}

.

(a)(i)

S O_{2}

gas is neutral in nature and thus there will be no change in colour of dry litmus paper.

(ii)

S O_{2}

reacts with water to produce

H_{2} S O_{3}

sulphurous acid that being acid turns blue moist litmus red.

(b)

S (s) + O_{2} (g) \to S O_{2} (g)

S O_{2} (g) + H_{2} O (a q) \to H_{2} S O_{3} (a q)

Answer

When sulphur is heated in air it produce sulphur dioxide

S O_{2}

.

(a)(i)

S O_{2}

gas is neutral in nature and thus there will be no change in colour of dry litmus paper.

(ii)

S O_{2}

reacts with water to produce

H_{2} S O_{3}

sulphurous acid that being acid turns blue moist litmus red.

(b)

S (s) + O_{2} (g) \to S O_{2} (g)

S O_{2} (g) + H_{2} O (a q) \to H_{2} S O_{3} (a q)

Question 9

State two ways to prevent the rusting of iron:

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Answer

1. Barrier protection:

In this method, a barrier film is introduced between iron and atmospheric oxygen and moisture. Barrier protection can be achieved

-By painting the surface

-By coating the surface with a thin film of oil or grease.

-By electroplating iron with some non-corrosive metal such as nickel, chromium, copper, etc.

2. Sacrificial protection:

In this method, surface of iron is covered with layer of more active metal like zinc. This active metal loses electrons (undergoes oxidation) in preference to iron and hence, prevents the rusting of iron.

Zinc metal is generally used for protecting iron and the process is called galvanization.

Answer

1. Barrier protection:

In this method, a barrier film is introduced between iron and atmospheric oxygen and moisture. Barrier protection can be achieved

-By painting the surface

-By coating the surface with a thin film of oil or grease.

-By electroplating iron with some non-corrosive metal such as nickel, chromium, copper, etc.

2. Sacrificial protection:

In this method, surface of iron is covered with layer of more active metal like zinc. This active metal loses electrons (undergoes oxidation) in preference to iron and hence, prevents the rusting of iron.

Zinc metal is generally used for protecting iron and the process is called galvanization.

Question 10

What type of oxides are formed when non-metals combine with oxygen?

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Answer

E x p l a n a t i o n :

The non-metals react with oxygen to form covalent compounds, which show acidic nature.

For example, sulphur reacts with oxygen gas to form sulphur dioxide. Sulphur dioxide shows acidic nature. it turns moist blue litmus paper to red.

S + O_{2} \to S O_{2}

S O_{2} + H_{2} O \to H_{2} S O_{3}

Therefore, we can say that acidic oxides are formed when non-metals combine with oxygen.

Answer

E x p l a n a t i o n :

The non-metals react with oxygen to form covalent compounds, which show acidic nature.

For example, sulphur reacts with oxygen gas to form sulphur dioxide. Sulphur dioxide shows acidic nature. it turns moist blue litmus paper to red.

S + O_{2} \to S O_{2}

S O_{2} + H_{2} O \to H_{2} S O_{3}

Therefore, we can say that acidic oxides are formed when non-metals combine with oxygen.

NCERT Solutions for Class 10 Chemistry Chapter 3 : Metals and Non metals

Access NCERT Solutions for Class 10 Chemistry Chapter 3 : Metals and Non metals

NCERT Solutions for Class 10 Chemistry Chapter 3 : Metals and Non metals

NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-Metals – Brief Overview

Element

Metals

Chemical Properties of Metals

Reactivity Series of Metals

Non-Metals

Chemical Properties of Non-Metals

Corrosion

Prevention of Corrosion

Frequently Asked Questions on NCERT Class 10 Chemistry Chapter 3 : Metals and Non metals