Chapter 3. Metals and Non-Metals

Class 10 Science Chapter 3. Metals and Non-Metals Multiple Choice Questions , 2 Marks Questions, 3 Marks Questions and Answers :

CBSE Previous Years Questions and Answers for 2008 

13. (a) What are amphoteric oxides ? Choose the amphoteric oxides from amongst the following oxides :

      , , ,  ,

(b) Why is it that non-metals do not displace hydrogen from dilute acids ?    [3M]

Answer : (a) Amphoteric oxides are oxides that can react with both acids and bases to form salts and water. They exhibit both acidic and basic properties.

The amphoteric oxides are  and  .

Non-metals do not displace hydrogen from dilute acids because they tend to form negatively charged ions by gaining electrons when reacting with metals. They also form oxides, which can be acidic or neutral. Non-metals instead react with hydrogen to form hydrides, rather than displacing it from acids.

CBSE Previous Years Questions and Answers for 2009

14. What is meant by rusting ? With labeled diagrams, describe an activity to find out the conditions under which iron rusts ? [3 M  2009 , 2020 ]

Answer : Rusting is the corrosion process that occurs when iron is exposed to moist air over an extended period. In this reaction, iron reacts with oxygen and water to form a brown, flaky substance known as rust.

Three test tubes labeled A, B, and C are prepared, each containing clean iron nails. Tube A contains water, Tube B has boiled distilled water with oil to prevent air dissolution, and Tube C includes anhydrous calcium chloride to absorb moisture. After leaving them for a few days, observe the conditions under which iron rusts. Tube A represents rusting in the presence of both air and water, Tube B indicates prevention of rusting with no dissolved air, and Tube C demonstrates prevention of rusting in dry air.

2. Name a reducing agent that may be used to obtain manganese from manganese dioxide . [1M 2009]

Answer :  Aluminium

CBSE Previous Years Questions and Answers for 2010

18. What is meant by refining of metals ? Name the most widely used method of refining impure metals produced by various reduction processes . Describe with the help of a labeled diagram how this method may be used for refining of copper . [2010 5M]

Answer : Refining of metals refers to the process of purifying or improving the quality of metals that are obtained from various reduction processes.

The most widely used method of refining impure metals produced by various reduction processes is electrolytic refining .

  

In the electrolytic refining process for copper, the setup involves an electrolyte solution of acidified copper sulphate. The anode consists of impure copper, while the cathode is a strip of pure copper. When an electric current is passed through the electrolyte, pure copper is deposited on the cathode. Impurities from the anode dissolve into the electrolyte, and pure metal from the electrolyte deposits onto the cathode. Soluble impurities enter the solution, while insoluble impurities settle as anode mud at the bottom. This process purifies copper effectively.

CBSE Previous Years Questions and Answers for 2011

1. A clear aluminium foil was placed in an aqueous solution of zinc sulphate . When the aluminium foil was taken out of the zinc sulphate solution after 15 minutes , its surface was found to be coated with a silvery grey deposit . From the above observation it can be concluded that : [2011 1M]

(a) Aluminium is more reactive than zinc

(b) Zinc is more reactive than aluminium

(c) Zinc and aluminium both are equally reactive

(d) Zinc and aluminium both are non-reactive

Answer :  (a) Aluminium is more reactive than zinc .

[ The silvery grey deposit observed on the surface of the aluminium foil indicates that aluminium has displaced zinc from the zinc sulphate solution. This suggests that aluminium is more reactive than zinc, as it can displace zinc from its salt solution through a single displacement reaction. ]

2. Iron nails were dipped in an aqueous solution of copper sulphate . After about 30 minutes . It was observed that the colour of the solution changed from   [2011 1M]

(a) Colorless to light green

(b) Blue to light green

(c) Blue to colourless

(d) Green to blue

Answer :  (c) Blue to colourless

[ When iron nails are dipped in an aqueous solution of copper sulphate, a displacement reaction occurs where iron displaces copper from the solution. This leads to the formation of iron sulphate solution and the removal of copper ions from the solution. As a result, the blue color of the copper sulphate solution fades away, leaving it colorless.]

CBSE Previous Years Questions and Answers for 2012

3. The colours of aqueous solutions of  and  as observed in the laboratory are : [2012 1M]

(a) Pale green and light blue respectively

(b) Light blue and dark green respectively

(c) Dark blue and dark green respectively

(d) Dark blue and pale green respectively

Answer :  (d) Dark blue and pale green respectively

[ In the laboratory, the aqueous solution of   (copper sulphate) typically appears dark blue, while the aqueous solution of  (iron sulphate) usually appears pale green. ]

4. A student prepared and aqueous solution of  in beaker X and  an aqueous solution of  in beaker Y. He then dropped some iron pieces in beaker X and some zinc pieces in beaker Y . After about 10 hours , he observed that the solution in X and Y respectively appears : [2012 1M]

(a) Blue and green

(b) Colourless and pale green

(c) Colourless and light blue

(d) Greenish and colourless

Answer : Colourless and pale green .

[ When iron pieces are added to a copper sulphate solution (CuSO₄), a displacement reaction occurs where iron displaces copper from the solution. This results in the formation of iron sulphate and the removal of copper ions, leading to a colorless solution.

Similarly, when zinc pieces are added to a ferrous sulphate solution (FeSO₄), a displacement reaction occurs where zinc displaces iron from the solution. This results in the formation of zinc sulphate and the removal of iron ions, leading to a pale green solution.

Therefore, after 10 hours, the solutions in beaker X and Y would be colorless and pale green, respectively.]

CBSE Previous Years Questions and Answers for 2018

19. (i) Write the steps involved in the extraction of pure metals in the middle of the activity series from their carbonate ores .

(ii) How is copper extracted from is sulphide ore ? Explain the various steps supported by chemical equations . Draw labeled diagram for the electrolytic refining of copper . [5M]

Solution : (i) The steps involved in the extraction of pure metals :

Carbonate ore → Calcination → Oxide of metal →Reduction to metal → Purification of metal

(i) Roasting : The sulphide ore concentrate is then roasted in the presence of excess oxygen. This converts the copper sulphide minerals into copper oxide and sulphur dioxide gas.

 

Again, Copper oxide is heated with sulphide ore, producing pure copper and sulphur dioxide gas

 

Electrolytic refining :   

 

Electrolytic refining for copper involves passing an electric current through a solution containing copper ions. At the cathode, pure copper is deposited, while impurities settle at the anode as sludge or dissolve into the electrolyte. This process ensures high purity copper suitable for various industrial applications.

CBSE Previous Years Questions and Answers for 2019

20. (i) List in tabular form three chemical properties on the basis of which we can differentiate between a metal and non-metal .

(ii) Given reasons for the following :

(a) Most metals conduct electricity well .

(b) The reaction of iron

(iii) oxide [ ] with heated aluminium is used to join cracked machine parts .[5M]

Answer : (i)  The difference between a metal and a non-metal lies in their chemical properties.

Property	Metal	Non-metal
Conductivity	Good conductors of electricity	Poor conductors of electricity
Reactivity	Generally lose electrons to form cations	Generally gain electrons to form anions
Metallic character	Typically shiny, malleable, and ductile	Not shiny, brittle when solid

(ii) (a)  Most metals conduct electricity well due to their ability to readily lose electrons, forming positive ions. This facilitates the flow of electrons within the metallic structure, enabling efficient electric current conduction.

(b) The reaction of iron(II) oxide [ ] with heated aluminum is utilized to join cracked machine parts through a thermite reaction.

The exothermic reaction produces molten iron and aluminum oxide, creating a strong, heat-welded joint.

CBSE Previous Years Questions and Answers for 2020

5. The compound obtained on reaction of iron with steam is/are :[1M]

(a)    (b)     (c) FeO  (d)  and  

Answer : (b)    

6. An element X reacts with  to give a compound with a high melting point . This compound is also soluble in water . The element X is likely to be :  [1M]

(a) Iron   (b) Calcium   (c) Carbon  (d) Silicon

Answer : (b) Calcium.

[ When calcium reacts with oxygen (), it forms calcium oxide (CaO), which has a high melting point and is also soluble in water, forming calcium hydroxide () when dissolved in water. ]

21. (a) What is thermit process ? where is this process used ? write balanced chemical equation for the reaction involved .

(b) Where does the metal aluminium , used in the process, occurs in the reactivity series of metals ?

(c) Name the substances that are getting oxidized and reduced in the process . [5M]

Answer : (a) The Thermit process is a type of exothermic oxidation-reduction chemical reaction that is used for the production of molten metal, typically iron. This process is often employed for welding purposes.

Use :   It is commonly used for welding railway tracks, where it helps create a strong and durable bond between the rail ends.

The typical reaction involves iron(III) oxide () reacting with aluminum (Al) to produce iron (Fe) and aluminum oxide ().

 

(b) Aluminum is a highly reactive metal and is not found free in nature. It occurs above iron in the reactivity series of metals.

(c) In the Thermit process, aluminum undergoes oxidation, and iron(III) oxide undergoes reduction.

 

Q. (a)  (i) Write two properties of gold which make it the most suitable metal for ornaments .

(ii) Name two metals which are the best conductors of heat .

(iii) Name two metals which melt when you keen them on your palm.

(b) Explain  the formation of ionic compound CaO with electron-dot structure . Atomic numbers of calcium and oxygen are 20 and 8 respectively . [5]

Answer : (i) Properties of Gold for Ornaments:  

(i) Gold does not tarnish, corrode, or rust, making it resistant to the effects of the environment and time. This property ensures that gold ornaments maintain their luster and appearance over extended periods.

(ii) Gold is highly malleable and ductile, meaning it can be easily shaped into intricate designs and drawn into thin wires without breaking. This makes it ideal for crafting detailed and delicate ornamentation.

(ii) Name of two metals which are the best conductors of heat are silver and copper .

(iii) Name of two metals which melt when you keen them on your palm are gallium and cesium .

(b) Formation of CaO :

Atomic number of Ca is 20

Electronic Configuration of Ca is 2.8.8.2

Atomic number of O is 8

Electronic Configuration of O is 2.6

CBSE Previous Years Questions and Answers for 2021

7. Which one of the following structure correctly depicts the compound  ?

Answer : (c)

8. The pairs which will show displacement reaction is/are

(i) NaCl solution and copper metal

(ii)  solution and copper metal

(iii)  solution and magnesium metal

(iv)   solution and iron metal

(a) (ii) only   (b) (ii) and (iii)   (c) (iii) and (iv)  (d) (i) and (ii)

Answer : (c) (ii) and (iii)  

[Therefore, the pairs that will show displacement reactions are: (ii)  solution and copper metal (iii)  solution and magnesium metal ]

Case Study Based Questions (Q.9 to Q.12) :

A student took four metals P,Q,R and S and carried out different experiments to study the properties of metals . Some of the observations were :

* All metals could not be cut with knife except metal R .

* Metal P combined with oxygen to from an oxide  which reacted with both acids and bases .

* Reaction with water .

P – Did not react either with cold or hot water but reacted with steam

Q – Reacted with hot water and the metal started floating

R – Reacted violently with cold water

S – Did not react with water at all

Based on the above observations answer the following questions :

9. Out of the given metals, the one which needs to be stored used kerosene is [1M]

(a) P   (b) R   (c)  S   (d)  Q

Answer :  (b) R

10. Out of the given metals, the metal Q is : [2021]

(a) Iron    (b) Zinc    (c) Potassium  (d) Magnesium

Answer :  (d) Magnesium

11. Metal which forms amphoteric oxides is :

(a) P     (b)  Q   (c) R    (d) S

Answer : (a) P

12. The increasing order of the reactivity of the four metals is :

(a) P<Q<R<S    (b) S<R<Q<P   (c) S<P<Q<R  (d) P<R<Q<S

Answer : (c) S<P<Q<R  

[ Note : Metal S does not react with water at all.

Metal P reacts with steam.

Metal Q reacts with hot water and floats.

Metal R reacts violently with cold water. Thus, the increasing order of reactivity is S<P<Q<R. Hence, the answer is (c) S<P<Q<R.]