Chapter 3: Metals and Non-Metals

Multiple Choose Questions and Answers

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.
Answer: (d)   solution and copper metal.

[ Copper is more reactive than silver in the reactivity series, so it can displace silver from silver nitrate solution. The reaction: Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag ]

Question: 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.

Answer: (c) Applying a coating of zinc.

[Zinc coating (galvanisation) protects iron by preventing its contact with air and moisture and also offers sacrificial protection. Zinc reacts preferentially, so the iron does not rust easily.]
Question: 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.

Answer:  (a) Calcium .

[Calcium reacts with oxygen to form calcium oxide (CaO), which has a high melting point due to strong ionic bonding. It reacts with water to form calcium hydroxide, which is soluble in water. Hence, calcium fits the given description.]
Question: 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.
Answer: (c) zinc is more reactive than tin.

[Zinc is more reactive than tin, so it can react with food materials and may form harmful compounds. Tin is less reactive and does not easily react with food, making it safer for coating food cans.]

Question: The compound obtained on reaction of iron with steam is/are :

(a)    (b)     (c) FeO  (d)  and  

Answer : (b)     

[When iron reacts with steam, it forms iron oxide Fe₃O₄ and hydrogen gas: 3Fe + 4H₂O (steam) → Fe₃O₄ + 4H₂ . Thus, Fe₃O₄ is the compound obtained.]

Question: 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 :

(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. ]

Question: 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 :

(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. ]

Question: 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

(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.]

Question: The colours of aqueous solutions of  and  as observed in the laboratory are :

(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. ]

Short Questions and Answers :

Question: What are amphoteric oxides? Give two examples of amphoteric oxides.
Answer: The metal oxides which react with both acids as well as bases to produce salts and water are called amphoteric oxides.  Example : and (Sodium aluminate) .

Question: Write equations for the reactions of
(i) iron with steam      (ii) calcium and potassium with water   [2M]

Answer: (i) When iron react with steam then produce iron oxide and  hydrogen gas .

 
(ii) When calcium react with water then produce calcium hydroxide and hydrogen gas .

 When potassium with water then produce potassium hydroxide and hydrogen gas .

Question: Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute  . [2M]

Answer: When dilute hydrochloric acid is added to a reactive metal then produce salt and hydrogen gas .

                    Metal + Dilute → Salt + Hydrogen gas .

When iron reacts with dilute  then produce iron(II) sulphate and hydrogen gas .

   
Question: What would you observe when zinc is added to a solution of iron(II) sulphate ? Write the chemical reaction that takes place.  [2M]

Answer: When zinc is added to a solution of iron(II) sulphate then produce zinc sulphate

    

Long Questionas and Answers :

Question: 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?
(ii) moist litmus paper?
(b) Write a balanced chemical equation for the reaction taking place.
Answer: When sulphur powder is heated, it burns in air to form sulphur dioxide (SO₂) gas.

(a) (i) On dry litmus paper, there will be no change, since acids or bases show effect only in the presence of water.
(ii) On moist litmus paper, SO₂ dissolves in water to form sulphurous acid (H₂SO₃), which turns blue litmus red (acidic action).

(b) Balanced chemical equation:

Question: 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. [3M]

Answer :  (a) The hammer can be used to test hardness and malleability: metals are generally hard and can be hammered into sheets, while non-metals are brittle and break easily. The battery, bulb, wires, and switch can be connected in a simple circuit to test conductivity: if the bulb glows when the sample is included, it is a conductor (metal); if not, it is an insulator (non-metal).

(b) These tests are useful as metals usually show both malleability and conductivity, while non-metals usually do not. However, exceptions exist: graphite (a non-metal) conducts electricity, and some metals like mercury are not hard. Thus, the tests are indicative but not conclusive.

Question:  (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  .

(b) 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.

Question:  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 . [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 .

Photo

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.

Question: (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]

Answer: (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 :     Photo   

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.

Question: (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 the presence of free electrons within their atomic structure. These electrons are loosely held and can move easily, facilitating the flow of electric current. This mobility of electrons allows metals to conduct electricity efficiently compared to materials with a more rigid electron arrangement.

(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.