Metals and Non - Metals
NCERT Solutions
NCERT Exercises
1. Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl_2 solution and aluminium metal
(c) FeSO_4 solution and silver metal
(d) AgNO_3 solution and copper metal.
AgNO_3 solution and copper metal.
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.
(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
(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.
(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?
With the given materials we are going to test two properties. One is the malleability and other is the conductivity. If we can make the given sample into a thin sheet by beating it with hammer, then that is a metal else it will be a non metal. By using the battery wires and bulb make a circuit with sample and test whether it conducts electricity or not. If it conducts electricity, then it is a metal other wise it is a non metal.
(b) Assess the usefulness of these tests in distinguishing between metals and nonmetals.
We can easily find the physical properties of metals and non metals using these tests.
6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Metal oxides that react with both acids and bases to produce salts and water are known as amphoteric oxides.
Examples of amphoteric oxides are PbO and SnO
7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Metals that are more reactive than hydrogen displace hydrogen from dilute acids. Examples are Sodium and Iron.
Metals that are less reactive than hydrogen do not displace hydrogen. Examples are Silver and Copper.
8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Anode → Impure metal M
Cathode → Pure metal M
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?
No reaction with the dry litmus paper.
ii. moist litmus paper?
Moist blue litmus paper turns into red. Here gas evolved is Sulphur dioxide which reacts with moisture to form sulphurous acid.
(b) Write a balanced chemical equation for the reaction taking place.
S(s) + O_2 (g) \rightarrow SO_2(g)
10. State two ways to prevent the rusting of iron.
i) By painting: Painting forms a layer between the iron and air/ water and this avoids air/ water come into direct contact with iron.
ii) Galvanization: An iron is coated with a layer of zinc metal.
11. What type of oxides is formed when nonmetals combine with oxygen?
Acidic oxides
12. Give reasons
(a) Platinum, gold and silver are used to make jewelers.
Because of their properties such as
- They are lustrous and malleable
- They are less reactive
(b) Sodium, potassium and lithium are stored under oil.
They are highly reactive metals and show vigorous reaction when it comes in contact with the air.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
Aluminium metal forms a thin layer of aluminium oxide all over its surface when it comes in contact with the oxygen in the air. This layer prevents the alumiinium from the further reaction. So that aluminium is now resistant to corrosion. It is also a good conductor of heat.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Extracting metals from their oxides are easier as compared to their carbonate and sulphides.
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.
Copper reacts with moist carbon dioxide in air and form copper carbonate. Presence of copper carbonate in the copper vessel results in losing its shiny brown surface and forming a green layer of copper carbonate. The citric acid in the lemon or tamarind neutralises the basis copper carbonate and dissolves the layer. That is why, tarnished copper vessels are cleaned with lemon or tamarind juice.
14. Differentiate between metals and non-metals.
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?
He must have dipped the gold in Aqua Regia. Aqua regia is a mixture of nitric acid and hydrochloric acid, which is in the ratio of 1:3. When we put gold in aqua regia the upper most layer gets dissolved in the solution and the inner layer comes out. That is why gold weighs less than before but is glitterier.
16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Copper does not react with water or steam, while iron reacts with steam to corrode the tank.
Intext Exercises
Pg. No. 40
1. Give an example of a metal which
(i) is a liquid at room temperature.
Mercury
(ii) can be easily cut with a knife.
Potassium
(iii) is the best conductor of heat.
Copper and Silver
(iv) is a poor conductor of heat.
Mercury.
2. Explain the meanings of malleable and ductile.
Malleable: It is the property of substance that can be beaten into thin sheets.
Ductile: Substance that can be drawn into thin wires.
Pg. No. 46
1. Why sodium is kept immersed in kerosene oil?
Sodium is a very reactive metal. Sodium reacts vigorously with air. So inorder to avoid such situation, sodium is kept immersed in kerosene oil.
2. Write equations for the reactions of
i. iron with steam
3Fe(s)+4H_2O(g) \rightarrow Fe_3O_4(s)+4H_2( g)
ii. calcium and potassium with water
Ca(s)+2H_2O(l) \rightarrow Ca(OH)_2(aq)+H_2( g)
2 K( s)+2H_2O(l) \rightarrow 2KOH(aq)+H_2( 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:
Use the Table above to answer the following questions about metals A, B, C and D.
i. Which is the most reactive metal?
Metal B is the most reactive metal
ii. What would you observe if B is added to a solution of Copper (II) sulphate?
When metal B is added to copper (II) sulphate solution, a displacement reaction will take place. During this reaction blue colour of copper (II) sulphate solution will fade and a red-brown deposit of copper will be formed on metal B.
iii. Arrange the metals A, B, C and D in the order of decreasing reactivity.
Decreasing order of reactivity of the metals is 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 H_2SO_4.
Hydrogen gas is produced when dilute hydrochloric acid is added to a reactive metal.
Chemical reaction when iron reacts with dilute H_2SO_4 is as shown below:
Fe(s)+H_2SO_4(aq) \rightarrow FeSO_4(aq)+H_2(g) .
5. What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.
Zinc is more reactive than iron, so that if we add zinc to solution of iron (II) sulphate, it would displace the iron from solution and forms a colorless solution of zinc sulphate.
Chemical reaction that takes place is shown below:
Zn(s)+FeSO_4(aq) \rightarrow ZnSO_4(aq)+Fe(s)
Pg. No. 49
1. Answer the following:
i. Write the electron-dot structures for sodium, oxygen and magnesium.
ii. Show the formation of Na_2O and MgO by the transfer of electrons.
Formation of Na_2O
Formation of MgO
iii. What are the ions present in these compounds?
The ions present in sodium oxide compound (Na2O): sodium ions (2Na+) and oxide ions (O2-). The ions present in Magnesium oxide compound (MgO): magnesium ions Mg2+ and oxide ions (O2-).
2. Why do ionic compounds have high melting points?
The electrostatic forces between ions in ionic compounds are strong. So it requires lot of energy to overcome these forces.
Pg. No. 53
1. Define the following terms.
i. Minerals: They are naturally occurring elements or compounds in earth’s crust.
ii. Ore: Mineral from which metals can be extracted.
iii. Gangue: Impurities, like sand, salt, soil etc, found in ore.
2. Name two metals which are found in nature in the free state
Gold and platinum
3. What chemical process is used for obtaining a metal from its oxide?
Reduction method is used for obtaining a metal from its oxide.
Pg. No. 55
1. Metallic oxides of zinc, magnesium and copper were heated with the following metals.
In which cases will you find displacement reactions taking place?
2. Which metals do not corrode easily?
Metals with less reactivity. Example silver, platinum and gold.
3. What are alloys?
An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.