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Important Questions of Metals and Non-Metals Class 10 Science Chapter 3
Question 1.
Reverse of the following chemical reaction is not possible:
Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
Justify this statement with reason. (Board Term I, 2016)
Answer:
If a strip of zinc metal is put in copper sulphate solution, then the blue colour of copper
sulphate fades gradually due to the formation of colourless zinc sulphate solution and
reddish-brown copper metal is deposited on zinc strip.
In this reaction, zinc metal being more reactive than copper displaces copper from copper
sulphate solution. If however, a strip of copper metal is placed in zinc sulphate solution, then
no reaction occurs. This is because copper metal is less reactive than zinc metal and hence,
cannot displace zinc from its salt solution.
Question 2.
Name a metal which:
(a) is the best conductor of heat.
(b) has a very low melting point.
(c) does not react with oxygen even at high temperature.
(d) is most ductile. (Board Term I, 2015)
Answer:
(a) Metal which is the best conductor of heat is silver.
(b) Gallium has a very low melting point.
(c) Silver and gold do not react with oxygen even at high temperature.
(d) Gold is the most ductile metal.
Question 3.
What is meant by amphoteric oxides? Choose the amphoteric oxides from the following :
Na2O, ZnO, CO 2, Al2O3, H2O (Board Term I, 2014)
Answer:
Amphoteric oxides are those which show acidic as well as basic character, i.e., they react
with bases as well as acids. ZnO and Al2O3 are amphoteric oxides.
Question 4.
Complete the following equation with balancing: (Board Term I, 2013)
(i) Al + HCl →
(ii) Mg + HNO 3 →
,Answer:
Question 5.
Compare in tabular form the reactivities of the following metals with cold and hot water:
(2020)
(a) Sodium
(b) Calcium
(c) Magnesium
Answer:
Question 6.
Give reason for the following:
(i) Hydrogen gas is not evolved when most of the metals react with nitric acid.
(ii) Zinc oxide is considered as an amphoteric oxide.
(iii) Metals conduct electricity. (Board Term I, 2016)
Answer:
(i) Hydrogen gas is not evolved when most metals react with nitric acid. It is because
HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself gets
reduced to any of the nitrogen oxides (N2O, NO, NO2).
, (ii) ZnO reacts both with acids as well as bases to form salt and water. Thus, ZnO is an
amphoteric oxide.
(iii) Metals conduct electricity due to the flow of free electrons present in them.
Question 7.
(a) Why does calcium start floating when it reacts with water? Write the balanced chemical
equation of the reaction.
(b) Name two metals which do not react with water. (Board Term I, 2015)
Answer:
(a) Calcium reacts with cold water to form calcium hydroxide and hydrogen gas.
The bubbles of hydrogen gas produced stick to the surface of calcium and hence, it starts
floating on the surface of water.
(b) Gold and silver do not react with water.
Question 8.
State what would happen if:
(i) some zinc pieces are placed in blue copper sulphate solution.
(ii) some’copper pieces are placed in green ferrous sulphate solution.
(iii) an iron nail is dipped in a solution of copper sulphate for some time. (Board Term I, 2014)
Answer:
(i) Refer to answer 1.
(ii) Cu + FeSO 4 No Reaction
Cu is less reactive than Fe, thus, it cannot displace Fe from FeSO 4 solution.
(iii) When an iron nail is dipped in copper sulphate solution, then the blue colour of copper
sulphate fades gradually and a reddish brown coating is formed on the iron nail.
As iron is more reactive than copper, it displaces copper from copper sulphate solution.
Question 9.
Give reason:
(a) Aluminium is a reactive metal but is still used for packing food articles.
(b) Calcium starts floating when water is added to it. (Board Term I, 2014)
Answer:
(a) Aluminium is a strong and cheap metal. It is also a good conductor of heat. But it is highly
reactive. When it is exposed to moist air, its surface is covered with a thin impervious layer of
aluminium oxide (Al2O3). This layer does not allow moist air to come in contact with the fresh
Important Questions of Metals and Non-Metals Class 10 Science Chapter 3
Question 1.
Reverse of the following chemical reaction is not possible:
Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
Justify this statement with reason. (Board Term I, 2016)
Answer:
If a strip of zinc metal is put in copper sulphate solution, then the blue colour of copper
sulphate fades gradually due to the formation of colourless zinc sulphate solution and
reddish-brown copper metal is deposited on zinc strip.
In this reaction, zinc metal being more reactive than copper displaces copper from copper
sulphate solution. If however, a strip of copper metal is placed in zinc sulphate solution, then
no reaction occurs. This is because copper metal is less reactive than zinc metal and hence,
cannot displace zinc from its salt solution.
Question 2.
Name a metal which:
(a) is the best conductor of heat.
(b) has a very low melting point.
(c) does not react with oxygen even at high temperature.
(d) is most ductile. (Board Term I, 2015)
Answer:
(a) Metal which is the best conductor of heat is silver.
(b) Gallium has a very low melting point.
(c) Silver and gold do not react with oxygen even at high temperature.
(d) Gold is the most ductile metal.
Question 3.
What is meant by amphoteric oxides? Choose the amphoteric oxides from the following :
Na2O, ZnO, CO 2, Al2O3, H2O (Board Term I, 2014)
Answer:
Amphoteric oxides are those which show acidic as well as basic character, i.e., they react
with bases as well as acids. ZnO and Al2O3 are amphoteric oxides.
Question 4.
Complete the following equation with balancing: (Board Term I, 2013)
(i) Al + HCl →
(ii) Mg + HNO 3 →
,Answer:
Question 5.
Compare in tabular form the reactivities of the following metals with cold and hot water:
(2020)
(a) Sodium
(b) Calcium
(c) Magnesium
Answer:
Question 6.
Give reason for the following:
(i) Hydrogen gas is not evolved when most of the metals react with nitric acid.
(ii) Zinc oxide is considered as an amphoteric oxide.
(iii) Metals conduct electricity. (Board Term I, 2016)
Answer:
(i) Hydrogen gas is not evolved when most metals react with nitric acid. It is because
HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself gets
reduced to any of the nitrogen oxides (N2O, NO, NO2).
, (ii) ZnO reacts both with acids as well as bases to form salt and water. Thus, ZnO is an
amphoteric oxide.
(iii) Metals conduct electricity due to the flow of free electrons present in them.
Question 7.
(a) Why does calcium start floating when it reacts with water? Write the balanced chemical
equation of the reaction.
(b) Name two metals which do not react with water. (Board Term I, 2015)
Answer:
(a) Calcium reacts with cold water to form calcium hydroxide and hydrogen gas.
The bubbles of hydrogen gas produced stick to the surface of calcium and hence, it starts
floating on the surface of water.
(b) Gold and silver do not react with water.
Question 8.
State what would happen if:
(i) some zinc pieces are placed in blue copper sulphate solution.
(ii) some’copper pieces are placed in green ferrous sulphate solution.
(iii) an iron nail is dipped in a solution of copper sulphate for some time. (Board Term I, 2014)
Answer:
(i) Refer to answer 1.
(ii) Cu + FeSO 4 No Reaction
Cu is less reactive than Fe, thus, it cannot displace Fe from FeSO 4 solution.
(iii) When an iron nail is dipped in copper sulphate solution, then the blue colour of copper
sulphate fades gradually and a reddish brown coating is formed on the iron nail.
As iron is more reactive than copper, it displaces copper from copper sulphate solution.
Question 9.
Give reason:
(a) Aluminium is a reactive metal but is still used for packing food articles.
(b) Calcium starts floating when water is added to it. (Board Term I, 2014)
Answer:
(a) Aluminium is a strong and cheap metal. It is also a good conductor of heat. But it is highly
reactive. When it is exposed to moist air, its surface is covered with a thin impervious layer of
aluminium oxide (Al2O3). This layer does not allow moist air to come in contact with the fresh
