NCERT Solutions for Class 10
Science
Chapter 3 – Metals and Non-Metals
INTEXT QUESTIONS:
1. Give an example of a metal which
i. Is a liquid at room temperature.
Ans: Mercury
ii. Can be easily cut with a knife.
Ans: Potassium
iii. Is the best conductor of heat.
Ans: Copper and Silver
iv. Is a poor conductor of heat.
Ans: Mercury.
2. Explain the meanings of malleable and ductile.
Ans: Malleable: Property of a metal due to which it can be beaten into thin sheets
is known as malleability and the metal is known to be malleable.
Ductile: Property of a metal due to which it can be beaten into thin pipes/wire is
known as ductility and the metal is known to be ductile.
INTEXT QUESTIONS:
1. Why sodium is kept immersed in kerosene oil?
Ans: Sodium is a very reactive metal. It reacts with the air and catches fire as soon
as it comes in contact with it. Hence, to avoid such accidents sodium is kept
immersed in kerosene oil.
2. Write equations for the reactions of
i. Iron with steam
Ans:
3Fe(s) 4H2O(g) Fe3O4(s) 4H2( g)
ii. Calcium and potassium with water
Ans:
Ca(s) 2H O(l) Ca(OH) (aq) H ( g) 2 2 2 2 2 2 K( s) 2H O(l) 2KOH(aq) H ( g)
heat
3. 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:
Metals Iron (II)
Sulphate
Copper (II)
Sulphate
Zinc
Sulphate
Silver
Nitrate
A No Reaction Displacement
B Displacement No Reaction
C No Reaction No Reaction No Reaction
D No Reaction No Reaction No Reaction No Reaction
Use the Table above to answer the following questions about metals A, B, C
and D.
Ans: According to the activity series the most reactive metal displaces the least
reactive metal. according to the given table we can say that:
A
is less reactive than iron but more reactive with copper.
A FeSO No reaction 4
A CuSO Single Displacement 4
B is more reactive than iron but less reactive than zinc.
B FeSO Single Displacement 4
B ZnSO No reaction 4
C
is less reactive than iron, copper and zinc but more reactive with silver
C FeSO No reaction 4
C CuSO No reaction 4
C ZnSO No reaction 4
C AgNO Single Displacement 3
D is less reactive than iron, copper,zinc, and silver
D FeSO No reaction 4
D CuSO No reaction 4
D ZnSO No reaction 4
D AgNO No Reaction 3
i. Which is the most reactive metal?
Ans: B is the most reactive metal.
B FeSO Single Displacement 4
ii. What would you observe if B is added to a solution of copper (II) sulphate?
Ans: When B is added to a solution of copper (II) sulphate then it shows the single
displacement because B is more reactive than iron.
B CuSO Single Displacement 4
iii. Arrange the metals A, B, C and D in the order of decreasing reactivity.
Ans:
B A C D
4. Which gas is produced when dilute hydrochloric acid is added to a reactive
metal? Write the chemical reaction when iron reacts with dilute
H2 4 SO .
Ans: Iron is more reactive than hydrogen according to the reactivity series. So,
when iron comes in contact with dilute
H SO2 4
it replaces hydrogen to form iron
sulphate and in the reaction it releases hydrogen gas.
Fe H SO FeSO ( ) 2 4( ) 4( ) 2( ) s aq aq g H
5. What would you observe when zinc is added to a solution of iron (II)
sulphate? Write the chemical reaction that takes place.
Ans: According to reactivity series we know zinc is more reactive than iron. So,
when zinc comes in contact with iron sulphate solution it replaces iron and forms
zinc sulphate. And the colour of solutions turns brown from green.
Zn FeSO ZnSO ( ) 4( ) 4( ) ( ) s aq aq s Fe
Intext Exercise :
1. Answer the following:
i. Write the electron-dot structures for sodium, oxygen and magnesium.
Ans: Sodium, oxygen and magnesium atomic numbers are 11, 8 and 12. The
electron dot structures are below:
Sodium (2,8,1) =
X
Na
Oxygen (2,6) =
Magnesium (2,8,2) =
XX
Mg
ii. Show the formation of
Na O2
and MgO by the transfer of electrons.
Ans: Both of the compounds will form an ionic bond.
iii. What are the ions present in these compounds?
Ans: In the
2 2 2 Na O, the ions 2Na and O - and in MgO are 2 Mg and O -
.
2. Why do ionic compounds have high melting points?
Ans: Ionic compounds have high electrostatic force between the molecules due to
which they are very closely packed and rigid. This tight packing results in ionic
compounds having high melting points.
Intext Exercise:
1. Define the following terms.
i. Minerals: :
Ans: The minerals which are present as a mixture of metallic compounds and
extractable impurities are known as ores and the compound of a metal found in
nature is called mineral.
ii. Ore:
Ans: The minerals from which the metals can be conveniently and economically
extracted are known as ores.
iii. Gangue:
Ans: The ore contains some impurities like sand, clay and rocky material. These
impurities are called gangue or matrix. Gangue is removed before the metallurgical
process starts.
2. Name two metals which are found in nature in the free state.
Ans: Silver and Gold are found in free state as their reactivity potential is very
low.
For example: Silver(Ag), Gold (Au), and Platinum(Pt).
3. What chemical process is used for obtaining a metal from its oxide?
Ans: More reactive metals are reduced by the electrolysis process. moderate
reactive metals can be reduced by either carbon or carbon monoxide. Metal oxides
are reduced by using suitable reducing agents such as carbon or by highly reactive
metals to displace the metals from their oxides. For example, zinc oxide is reduced
to metallic zinc by heating with carbon.
ZnO Zn CO ( ) ( ) ( ) ( ) s s s g C
or
ZnO CO Zn CO 2
Thermite process: Chromium oxides are reduced to chromium by treating it with
aluminium powder. In this case, aluminium displaces manganese from its oxide
Cr O 2Al Al O 2Cr heat 2 3 2 3
Intext Exercise
1. Metallic oxides of zinc, magnesium and copper were heated with the
following metals.
Metals Zinc Magnesium Copper
Zinc Oxide - - -
Magnesium Oxide - - -
Copper Oxide - - -
In which cases will you find displacement reactions taking place?
Ans:
Metals Zinc Magnesium Copper
Zinc Oxide No reaction Displacement No reaction
Magnesium Oxide No reaction No reaction No reaction
Copper Oxide Displacement Displacement No reaction
2. Which metals do not corrode easily?
Ans: Metals with less reactivity such as silver, platinum and gold.
3. What are alloys?
Ans: An alloy is a homogenous mixture of two metals or metal and non-metals.
They are formed by melting the metals and mixing them and then solidifying them
into alloy.
Example: Bronze is an alloy of copper and tin.
EXERCISE QUESTIONS
1. Which of the following pairs will give displacement reactions?
(a)
NaCl
solution and copper metal
(b)
MgCl2
solution and aluminium metal
(c)
FeSO4
solution and silver metal
(d)
AgNO3
solution and copper metal.
Ans: (d)
AgNO3
solution and copper
2. Which of the following methods is suitable for preventing an iron frying
pan from rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) all of the above.
Ans: (c) Applying a coating of zinc
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
(b) carbon
(c) silicon
(d) iron
Ans: (a) calcium
4. Food cans are coated with tin and not with zinc because
(a) zinc is costlier than tin.
(b) zinc has a higher melting point than tin.
(c) zinc is more reactive than tin.
(d) zinc is less reactive than tin.
Ans: (c) zinc is more reactive than tin.
5. You are given a hammer, battery, bulb, wires and a switch.
(a) How could you use them to distinguish between samples of metals and non-
metals?
Ans: Metals are naturally malleable. We can beat the given sample with the help of
a hammer. If it turns into thin sheets, it is metal; otherwise, it is nonmetal.
Metals carry electricity. when we use a battery, a lamp, wires, and a switch to
create a circuit. If the bulb glows, it indicates that the sample is metallic due to
liberated electrons. If the bulb does not light up, this indicates that the sample is
non-metallic.
(b) Assess the usefulness of these tests in distinguishing between metals and
nonmetals.
Ans: The physical properties of metals and non-metals are represented by these
tests. We can easily distinguish between them based on their physical
characteristics
6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Ans: Oxides which can react with both acid and base is known as amphoteric
oxide.
Example: Zinc oxide
( ) ZnO
and Aluminum oxide
Al O2 3
7. Name two metals which will displace hydrogen from dilute acids, and two
metals which will not.
Ans: More reactive metals will displace hydrogen from its dilute acids. for
example : Iron and Zinc.
Fe 2HCl FeCl H 2 2 Zn 2HCl ZnCl H 2 2
Least reactive metals will not displace hydrogen from its dilute acids. for example :
copper and silver
Cu HCl
No Reaction
Ag HCl
No Reaction
8. In the electrolytic refining of a metal M, what would you take as the anode,
the cathode and the electrolyte?
Ans: In the electrolytic refining of a metal M:
i. Cathode → Pure metal M
ii. Anode → Impure metal M
iii. Electrolyte → Salt Solution of the metal M
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 below.
(a) What will be the action of gas on
i. Dry litmus paper?
Ans: No reaction with dry litmus paper.
ii. Moist litmus paper?
Ans: Moist blue litmus will turn red due to the formation of sulphur dioxide.
Sulphur dioxide is acidic oxide when it will react with water converts into
sulphurous acid.
(b) Write a balanced chemical equation for the reaction taking place.
Ans:
S O SO ( ) 2( ) 2( ) s g g
2( ) 2 ( ) 2 3( ) Sulphur dioxide
SO H O H SO g l aq
10. State two ways to prevent the rusting of iron.
Ans: The process of degrading metals in presence of air and water is known as
rusting. Two ways in which rusting can be prevented are as follows:
i. Painting: It prevents iron from coming in direct contact with air and water.
ii. Galvanization: In this process iron is coated with a layer of zinc.
11. What type of oxides is formed when non-metals combine with oxygen?
Ans: Non-metals combines with oxygen and forms acidic oxides which when
combined with water turns into acidic solution.
12. Give reasons
(a) Platinum, gold and silver are used to make jewellers.
Ans: These metals are very less reactive and are lustrous which makes them
suitable for making jewellry.
(b) Sodium, potassium and lithium are stored under oil.
Ans: They are highly reactive metals and catch fire as soon as it comes in contact
with the air. Hence, to avoid any accidents these metals are kept under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for
cooking.
Ans: Aluminium is highly reactive and they react with oxygen present in
atmosphere to form a stable compound
Al O2 3
. Along with this, they are very good
conductor of heat. Therefore, aluminium is used in making utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the
process of extraction.
Ans: Extracting metals from their oxides are easier as compared to their carbonate
and sulphides. Therefore, ores are usually converted into oxides by the process of
roasting and calcination.
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.
Ans: Copper forms basic copper carbonate
3 2 (CuCO .Cu(OH) )
when it combines
with damp carbon dioxide in the air. It turns green, and the copper vase loses its
gleaming brown finish. The presence of citric acid in the lemon or tamarind
neutralizes the basic copper carbonate and dissolves the layer.
14. Differentiate between metals and non-metals.
Ans: Differences between metals and non-metals are as follows:
METALS NON-METALS
Metals are electropositive. Non-metals are electronegative.
They react with water to form oxides
and hydroxides. Some metals react with
cold water, some with hot water, and
some with steam.
2 2 2Na 2H O 2NaOH H
They do not react with water.
They react with oxygen to form basic
oxides
2 2 4Na O 2Na O
These have ionic bonds.
They react with oxygen to form acidic
or neutral oxides.
C O CO 2 2
These have covalent bonds
They react with dilute acids to form a
salt and evolve hydrogen gas. However,
Cu, Ag, Au, Pt, Hg do not react.
2
2Na 2HCl 2NaCl H .
They do not react with dilute acids.
These are not capable of replacing
hydrogen.
They react with the salt solution of
metals. Depending on their reactivity,
These react with the salt solution of non-
metals
displacement reaction can occur
CuSO Zn ZnSO Cu 4 4 .
They act as reducing agents.
Na Na e
These act as oxidizing agents.
Cl 2e 2Cl 2
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?
Ans: The man is using Aqua Regia which is 3 parts of
HCL
and 1 part of
HNO3
solution. Gold is least reactive metal but when we put it in aqua regia the upper
most layer and gets dissolved in the solution and the inner layer comes out due to
which it weighs less than before but are glitterier.
16. Give reasons why copper is used to make hot water tanks and not steel (an
alloy of iron).
Ans: In the reactivity reaction copper comes below hydrogen and hence, it will not
react with the water present/stored. On the other hand, steel which is an alloy of
iron will react with the steam and can get corroded easily.
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