Selina Class 8 ICSE Solutions Chemistry : Chapter 5- Language of Chemistry Solutions

Class 8: Chemistry Chapter 5 solutions. Complete Class 8 Chemistry Chapter 5 Notes.

Selina Class 8 ICSE Solutions Chemistry : Chapter 5- Language of Chemistry Solutions

Selina 8th Chemistry Chapter 5, Class 8 Chemistry Chapter 5 solutions

ACTIVITY 1

Write the names and symbols of the first twenty elements that you have studied in class VI & VII.

Answer:

Name of the elements	Symbol	Valency
1. Hydrogen 2. Helium 3. Lithium 4. Beryllium 5. Boron 6. Carbon 7. Nitrogen 8. Oxygen 9. Fluorine 10. Neon 11. Sodium 12. Magnesium 13. Aluminium 14. Silicon 15. Phosphorus 16. Sulphur 17. Chlorine 18. Argon 19. Potassium 20. Calcium	H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca	1 0 1 2 3 4 3 2 1 0 1 2 3 4 3 2 1 0 1 2

ACTIVITY 2

Write the molecular formulae of:

1. Copper oxide

Answer: CuO

2. Iron (III) chloride

Answer: FeCl₃

3. Sodium hydroxide

Answer: NaOH

4. Iron (II) sulphide

Answer: FeS

5. Lead (II) oxide

Answer: PbO

6. Hydrogen nitrate (nitric acid)

Answer: HNO₃

7. Hydrogen sulphate (sulphuric acid)

Answer: H₂SO₄

8. Calcium hydroxide

Answer: Ca(OH)₂

9. Magnesium carbonate

Answer: MgCO₃

10. Ammonium carbonate

Answer: (NH₄)₂CO₃

ACTIVITY 3

Write the molecular formula for each of the following compounds:

1. Sulphur trioxide

2. Iron (II) sulphide

3. Ammonia

Find the number and names of elements present in them and calculate their molecular masses.

Answer:

1. Sulphur trioxide

1. The molecular formula of sulphur trioxide is SO₃.

2. The elements present in it are sulphur dioxide and oxygen.

3. One molecule of sulphur trioxide has one atom of sulphur and three atoms of oxygen.

4. The molecular mass of sulphur trioxide SO₃

=32+3×16

=32+48=80 amu

2. Iron (II) sulphide

1. The molecular formula of iron (II) sulphide is FeS.

2. The elements present in it are iron and sulphur.

3. One molecule of iron (lI) sulphide has one atom of iron and one atom of sulphur.

4. The molecular mass of iron (II) sulphide (FeS)

= 55.5+32

=87.5 amu

3. Ammonia

1. The molecular formula of ammonia is NH₃.

2. The elements present in it are nitrogen and hydrogen.

3. One molecule of ammonia has one atom of nitrogen and three atoms of hydrogen.

4. The molecular mass of ammonia(NH₃)

=14+3×1

=14+3

=17 amu

Question 1

Define:

(a) Radical

(b) Valency

(c) Molecular formula

Solution:

(a) Radical: An atom of an element or a group of atoms of different elements that behaves as a single with a positive or negative charge on it is called radical.

(b) Valency: The number of electrons donated or accepted by the valence shell of an atom during chemical combination is called as valency.

(c) Molecular formula: Molecular formula is a symbolic representation of a molecule. It represents the number of atoms of each element present. These atoms combine in the whole to form the molecule.

Question 2.

Give the symbols and valencies of the following radicals:

(a) Hydroxide

(b) Chloride

(c) Carbonate

(d) Ammonium

(e) Nitrate

Solution:

Element	Symbol	Valencies
(a) Hydroxide (b) Chloride (c) Carbonate (d) Ammonium (e) Nitrate	OH– Cl– CO23- NH4+ NO3–	1 1 2 1 1

Question 3.

Write the molecular formula for the oxide and sulphide of the following elements.

(a) Sodium

Solution:

(a) Sodium oxide Na₂O

Sodium sulphide Na₂S

(b) Calcium

Solution:

(b) Calcium oxide CaO

Calcium sulphide CaS

(c) Hydrogen

Solution:

(c) Hydrogen oxide H₂O

Hydrogen sulphide H₂S

Question 4.

Write the molecular formulae for the following compounds and name the elements present.

(a) Baking soda

Solution:

(a) Baking soda- NaHCO₃

Elements present in Baking soda are sodium, hydrogen, oxygen and carbon.

(b) Common salt

Solution:

(b) Common salt – NaCl

Elements present in common salt are Sodium and chlorine.

(c) Sulphuric acid

Solution:

(c) Sulphuric acid – H₂SO₄

Elements present in Sulphuric acid are Hydrogen, sulphur and oxygen.

(d) Nitric acid

Solution:

(d) Nitric acid – HNO₃

Elements present in Nitric acid are Hydrogen, nitrogen and oxygen.

Question 5.

The valency of aluminium is 3. Write the valency of other radicals present in the following compounds.

(a) Aluminium chloride

Solution:

(a) The molecular formula of Aluminium chloride- AlCl₃

Valency of Al is 3.

Another radical present is chloride (Cl^–) and its valency is 1.

(b) Aluminium oxide

Solution:

(b) The molecular formula of Aluminium oxide – Al₂O₃

Valency of Al is 3

Another radical present is an oxide (O^2-) and its valency is 2.

(c) Aluminium nitride

Solution:

(c) The molecular formula of Aluminium nitride –(AlN)

Valency of aluminium is 3

Another radical present is Nitride (N^3-) and its valency is 3

(d) Aluminium sulphate

Solution:

(d) The molecular formula of aluminium sulphate – (Al₂SO₄)₃

Valency of aluminium is 3

Another radical present is sulphate (SO₄^-2) and its valency is 2.

Question 6.

What is the variable valency? Give two examples of elements showing variable valency.

Solution:

Some elements have multiple valencies that mean they show variable valency.

Ferrous is written as Iron (II), and Ferric is written as Iron (III).

Metal	Radicals	Valency
Iron	Ferrous [iron (II)] Ferric [iron (III)]	2 3
Copper	Cuprous [copper (I)] Cupric [copper (II)]	1 2

Question 7

(a) What is the chemical equation?

Solution:

(a) Chemical Equation- The symbolic representation of a chemical reaction using the symbols and the formulae of the substances involved in the reaction is called as a chemical equation.

(b) Why is it necessary to balance a chemical equation?

Solution:

(b) The chemical equation needs to be balanced to make the number of the atoms of the reactants equal to the number of the atoms of the products

(c) What are the limitations of a chemical equation?

Solution:

1. It does not state anything about the physical states of the product and the reactants, i.e. whether they are solids, liquids and gases.

2. It does not say anything about the concentration of reactants and products.

3. It does not inform about the time taken for the completion of the reaction.

4. It does not inform about the rate at which a reaction proceeds.

5. It does not inform about the heat changes during the reaction, i.e. whether the heat is given out of absorbed.

6. It does not inform about the conditions such as temperature, pressure, catalyst etc. which affect the reaction.

7. It does not inform about the nature of the reaction, i.e. whether it is reversible or irreversible..

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Selina Class 8 ICSE Solutions Chemistry : Chapter 5- Language of Chemistry Solutions

Download PDF: Selina Class 8 ICSE Solutions Chemistry : Chapter 5- Language of Chemistry Solutions PDF

Chapterwise Selina Publishers ICSE Solutions for Class 8 Chemistry :

• Chapter 1- Matter
• Chapter 2- Physical and Chemical Changes
• Chapter 3- Elements, Compounds and Mixtures
• Chapter 4- Atomic Structure
• Chapter 5- Language of Chemistry Solutions
• Chapter 6- Chemical Reactions Solutions
• Chapter 7- Hydrogen Solutions
• Chapter 8- Water Solutions
• Chapter 9- Carbon and Its Compounds

About Selina Publishers ICSE

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