Periodic Classification of Elements: Class 10 Science Book Back Answers

Book Back Questions with Answers - Periodic Classification of Elements

I. Choose the best answer.

1. The number of periods and groups in the periodic table are______.

• a) 6,16
• b) 7,17
• c) 8,18
• d) 7,18

2. The basis of modern periodic law is______.

• a) atomic number
• b) atomic mass
• c) isotopic mass
• d) number of neutrons

3. _____ group contains the member of halogen family.

• a) 17^th
• b) 15^th
• c) 18^th
• d) 16^th

4. _____ is a relative periodic property

• a) atomic radii
• b) ionic radii
• c) electron affinity
• d) electronegativity

5. Chemical formula of rust is ________.

• a) FeO.xH₂O
• b) FeO₄.xH₂O
• c) Fe₂O₃.xH₂O
• d) FeO

6. In the alumino thermic process the role of Al is _____.

• a) oxidizing agent
• b) reducing agent
• c) hydrogenating agent
• d) sulphurising agent

7. The process of coating the surface of metal with a thin layer of zinc is called______.

• a) painting
• b) thinning
• c) galvanization
• d) electroplating

8. Which of the following have inert gases 2 electrons in the outermost shell.

• a) He
• b) Ne
• c) Ar
• d) Kr

9. Neon shows zero electron affinity due to _____.

• a) stable arrangement of neutrons
• b) stable configuration of electrons
• c) reduced size
• d) increased density

10. ______ is an important metal to form amalgam.

• a) Ag
• b) Hg
• c) Mg
• d) Al

II. Fill in the blanks

1. If the electronegativity difference between two bonded atoms in a molecule is greater than 1.7, the nature of bonding is ionic.

2. 6^th is the longest period in the periodical table.

3. Atomic number forms the basis of modern periodic table.

4. If the distance between two Cl atoms in Cl₂ molecule is 1.98Å, then the radius of Cl atom is 0.99 Å.

5. Among the given species A^–, A⁺, and A, the smallest one in size is A⁺.

6. The scientist who propounded the modern periodic law is Henry Moseley.

7. Across the period, ionic radii decreases (increases,decreases).

8. Lanthanides and Actinides are called inner transition elements.

9. The chief ore of Aluminium is Bauxite.

10. The chemical name of rust is hydrated ferric oxide.

III. Match the following

Question:

• 1. Galvanisation : Noble gas elements
• 2. Calcination : Coating with Zn
• 3. Redox reaction : Silver-tin amalgam
• 4. Dental filling : Alumino thermic process
• 5. Group 18 elements : Heating in the absence of air

Answer:

• 1. Galvanisation Coating with Zn
• 2. Calcination Heating in the absence of air
• 3. Redox reaction Alumino thermic process
• 4. Dental filling Silver-tin amalgam
• 5. Group 18 elements Noble gas elements

IV. True or False: (If false give the correct statement)

1. Moseley’s periodic table is based on atomic mass.

False.

Correct Statement: Moseley's periodic table is based on atomic number.

2. Ionic radius increases across the period from left to right.

False.

Correct Statement: Ionic radius decreases across the period from left to right.

3. All ores are minerals; but all minerals cannot be called as ores.

True.

4. Al wires are used as electric cables due to their silvery white colour.

False.

Correct Statement: Al wires are used in electric cables as they are good conductors of electricity.

5. An alloy is a heterogenous mixture of metals.

False.

Correct Statement: An alloy is a homogeneous mixture of metals.

V. Assertion and Reason

Answer the following questions using the data given below:

• i. A and R are correct, R explains the A.
• ii. A is correct, R is wrong.
• iii. A is wrong, R is correct.
• iv. A and R are correct, R doesn’t explains A.

1.

Assertion: The nature of bond in HF molecule is ionic.

Reason: The electronegativity difference between H and F is 1.9.

i. A and R are correct, R explains the A.

2.

Assertion: Magnesium is used to protect steel from rusting.

Reason: Magnesium is more reactive than iron.

iii. A is wrong, R is correct.

3.

Assertion: An uncleaned copper vessel is covered with greenish layer.

Reason: copper is not attacked by alkali.

i. A and R are correct, R explains the A.

VI. Short answer questions

1. A is a reddish brown metal, which combines with O₂ at < 1370 K gives B, a black coloured compound. At a temperature > 1370 K, A gives C which is red in colour. Find A, B and C with reaction.

Reddish brown metal A is copper.

2. A is a silvery white metal. A combines with O₂ to form B at 800°C, the alloy of A is used in making the aircraft. Find A and B.

Silvery white metal is aluminium.

3. What is rust? Give the equation for formation of rust.

When iron is exposed to moist air, it forms a layer of brown hydrated ferric oxide on its surface. This compound is known as rust and the phenomenon of formation of rust is known as rusting.

4Fe + 3O2 + xH2O → 2Fe2O3.xH2O (rust)

4. State two conditions necessary for rusting of iron.

Two conditions necessary for rusting iron are (i) Oxygen and (ii) Water.

VII. Long answer questions

1. a) State the reason for addition of caustic alkali to bauxite ore during purification of bauxite.

b) Along with cryolite and alumina, another substance is added to the electrolyte mixture. Name the substance and give one reason for the addition.

a) Caustic soda solution at 150°C is added to bauxite ore to obtain Sodium Meta Aluminate.

b) Fluorspar is added to the electrolyte mixture so as to lower the fusion temperature of the electrolyte.

2. The electronic configuration of metal A is 2,8,18,1. The metal A when exposed to air and moisture forms B a green layered compound. A with con. H₂SO₄ forms C and D along with water. D is a gaseous compound. Find A, B, C and D.

Metal A is copper.

2Cu + O2 + CO2 + H2O → CuCO3.Cu(OH)2

2Cu [A:Copper] + O2 + CO2 + H2O → CuCO3.Cu(OH)2 [B:Basic copper carbonate]

Cu + 2H2SO4 → CuSO4 + SO2 ↑ + H2O

Cu [A:Copper] + 2H2SO4 → CuSO4 [C:Copper sulphate] + SO2 ↑ [D:Sulphur-di-oxide] + H2O

[A: Cu : Copper]

[B: CuCO₃.Cu(OH)₂ : Basic copper carbonate]

[C: CuSO₄ : Copper sulphate]

[D: SO₂ : Sulphur-di-oxide]

3. Explain smelting process.

Smelting: Smelting is the process of reducing the roasted metallic oxide from the metal in its molten condition. In this process, impurities are removed as slag by the addition of flux.

VIII. HOT questions

1. Metal A belongs to period 3 and group 13. A in red hot condition reacts with steam to form B. A with strong alkali forms C. Find A, B and C with reactions.

Metal A is Aluminium.

2Al + 3H2O → Al2O3 + 3H2

2Al [(A) Aluminium] + 3H2O → Al2O3 [(B) Aluminium oxide] + 3H2

2Al + 2NaOH + 2H2O → 2NaAlO2 + 3H2 ↑

2Al + 2NaOH + 2H2O → 2NaAlO2 [C: Sodium meta aluminate] + 3H2 ↑

(A) : Al : Aluminium

(B) : Al₂O₃ : Aluminium oxide

(C) : 2NaAlO₂ : Sodium meta aluminate

2. Name the acid that renders aluminium passive. Why?

Dilute or concentrated nitric acid does not attack aluminium, but it renders aluminium passive due to the formation of an oxide film on its surface.

3. a) Identify the bond between H and F in HF molecule.

b) What property forms the basis of identification?

c) How does the property vary in periods and in groups?

a) Ionic bond

b) Electronegativity

c) Along the period, from left to right in the periodic table, the electronegativity increases. On moving down a group, the electronegativity of the elements decreases.

Concept Map

Occurrence of Ores in Tamil Nadu | 10th Science Chapter 8

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

10th Science : Chapter 8 : Periodic Classification of Elements : Occurrence of Ores in Tamil Nadu |

Occurrence of Ores in Tamil Nadu

Chapter: 10th Science : Chapter 8 : Periodic Classification of Elements

(Reference: mineral resources of Tamil Nadu-ENVIS Centre, Tamil Nadu)

OCCURRENCE OF ORES IN TAMIL NADU

• Lime stone: Coimbatore, Cuddalore, Dindugul
• Gypsum: Tiruchi and Coimbatore Distiricts
• Titanium minerals: Kanyakumari, Tirunelveli and Tuticorin.
• Chromite: Coimbatore and Salem district.
• Magnetite: Dharmapuri, Erode, Salem, Thiruvannamalai.
• Tungsten: Madurai and Dindugal.

(Reference: mineral resources of Tamil Nadu-ENVIS Centre, Tamil Nadu)

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

10th Science : Chapter 8 : Periodic Classification of Elements : Occurrence of Ores in Tamil Nadu |

Understanding Metallurgy: Key Terminology and Ore Concentration Methods

Metallurgy - Terminology, Types of separation or concentration of an ore

METALLURGY

Human life is associated with various metals. We use metals in our day to day activities. It is the utmost need to have some metals like sodium, potassium, calcium, iron, etc. in the human body. Deficiency of these metals affects the metabolic activities thereby causing diseases. So, metals play a vital role in our life. In this section, let us discuss how metals are obtained from various sources by the process of metallurgy.

Metallurgy is a science of extracting metals from their ores and modifying the metals into alloys for various uses, based on their physical and chemical properties and their structural arrangement of atoms. A metallurgical process involve three main steps as follows:

(i) Concentration or Separation of the ore: It is the process of removal of impuries from the ore.

(ii) Production of the metal: It is the conversion of the ore into metal.

(iii) Refining of the metal: It is the process of purification of the metal.

1. Terminology in metallurgy

Minerals: A mineral may be a single compound or a complex mixture of various compounds of metals found in the Earth.

Ore: The mineral from which a metal can be readily and economically extracted on a large scale is said to be an ore.

For example: Clay (Al₂O₃. 2 SiO₂. 2 H₂O) and bauxite (Al₂O₃ .2 H₂O) are the two minerals of aluminium, but aluminium can be profitably extracted only from bauxite. Hence, bauxite is an ore of aluminium and clay is its mineral.

Mining: The process of extracting the ores from the Earth's crust is called mining.

Gangue or Matrix: The rocky impurity associated with an ore is called gangue or matrix.

Flux: It is the substance added to the ore to reduce the fusion temperature and to remove the impurities. E.g. Calcium oxide (basic), Silica (acidic). If the gangue is acidic, then basic flux is added and vice versa.

Slag: It is the fusible product formed when a flux reacts with a gangue during the extraction of metals.

Flux + Gangue → Slag

Smelting: Smelting is the process of reducing the roasted metallic oxide from the metal in its molten condition. In this process, impurities are removed as slag by the addition of flux.

2. Types of separation or concentration of an ore

There are four major types of separation of ores based on the nature of the ore. The different kinds of ores of metals are given in Table 8.1

Concentration of the crushed ore is done mainly by the following methods: -

(i) Hydraulic (Gravity Separation) method

Principle:

The difference in the densities or specific gravities of the ore and the gangue is the main principle behind this method. Oxide ores are purified by this method. e.g., Haematite Fe₂O₃ the ore of iron.

Method:

The ore is poured over a sloping,vibrating corrugated table with grooves and a jet of water is allowed to flow over it. The denser ore particles settle down in the grooves and lighter gangue particles are washed down by water.

(ii) Magnetic separation method

Principle:

The magnetic properties of the ores form the basis of separation. When either the ore or the gangue is magnetic, this method is employed. e.g., Tinstone SnO₂, the ore of tin.

Method: The crushed ore is placed over a conveyer belt which rotates around two metal wheels, one of which is magnetic. The magnetic particles are attracted to the magnetic wheel and fall separately apart from the non- magnetic particles.

(iii) Froth floatation

Principle:

This process depends on the preferential wettability of the ore with oil (pine oil) and the gangue particles by water. Lighter ores, such as sulphide ores, are concentrated by this method. e.g., Zinc blende (ZnS).

Method:

The crushed ore is taken in a large tank containing oil and water and agitated with a current of compressed air. The ore is wetted by the oil and gets separated from the gangue in the form of froth. Since the ore is lighter, it comes on the surface with the froth and the impurities are left behind. e.g., Zinc blende (ZnS).

(iv) Chemical method or Leaching

This method is employed when the ore is in a very pure form.

Extraction of metal from metal oxide can be categorized into three types.

The ore is treated with a suitable reagent such that the ore is soluble in it but the impurities are not. The impurities are removed by filtration. The solution of the ore, ie., the filtrate is treated with a suitable reagent which precipitates the ore. E.g. Bauxite Al₂O₃.2H₂O, the ore of aluminium.

Metallurgy

Ans. The process of extraction of metals from their ores, refining, and alloying them is called metallurgy. The three important steps involved in the extraction of metals from their ores are:

1. Preliminary treatment: - In the preliminary treatment, the gangue is removed to concentrate the ore.
2. Chemical reduction: - The reduction can be brought about in two ways:
1. The reducing agent reduces the metal oxide to metal.
2. The reduction by electrolysis.
3. Refining: - The metal obtained by chemical reduction contains impurities. The impure metal is purified. 

Define

1.     Allotropy: - The property by which an element exists in tow or more crystalline forms is called allotropy.

2.     Alloy: - An alloy is a homogeneous mixture of two or more metals or metal and a nonmetal.

3.     Calcinations: - The process of strongly heating the concentrated ore in the limited supply of air and converting into its oxide is called calcinations.

4.     Dry ice: - Solid carbon dioxide is called dry ice.

5.     Ductility: - The property of a metal due to which it can be drawn into a wire is called ductility.

6.     Gangue: - The unwanted material present in an ore is called gangue. For example impure sand and rocky material in an ore.

7.     Malleability: - The property of a metal due to which it can be hammered into a thin sheet without cracking is called malleability.

8.     Metal: - The element which can form positive ions by the loss of electrons is called metal. Iron and copper are metals.

9.     Metallurgy: - The process of extraction of metals from their ores, refining, and alloying them is called metallurgy.

10.  Metalloid: - The element which shows the properties of metals as well as those of nonmetals is called a metalloid. Arsenic and antimony are metalloids.

11.  Milk of sulphur: - Sulphur obtained by chemical reaction as precipitate is called milk of sulphur.

12.  Mineral: - A mineral is a material in the earth’s crust in which elements and compounds of inorganic nature are formed naturally.

13.  Nonmetal: - The element which can form negative ions by the gain of electrons is called nonmetal. Phosphorus and sulphur are nonmetals.

14.  Ore: - The mineral from which a metal can be extracted profitably is called an ore.

15.  Pig iron: - The iron which is obtained from the blast furnace is called cast or pig iron. It contains carbon as major impurity upto 4%.

16.  Reduction: - The chemical reaction in which oxygen is removed from a compound is called reduction. Or the conversion of metal ion into elemental metal is called reduction. Or the process of obtaining a metal from its oxides is called reduction.

17.  Refining: - The process of purification of an impure metal is known as refining of the metal.

18.  Roasting: - The process of heating the concentrated ore to a high temperature in excess of air, and converting into its oxide is called roasting. 

Metallurgy

Metallurgy: - The process used for extraction of metals in their pure form from their ores is called metallurgy.