Selina Textbook Solutions: Language of Chemistry | Chemistry Class 9 ICSE PDF Download

 Page 1


Chapter 4. The Language of Chemistry
Exercise 4
Solution 1.
Solution 2.
Solution 3.
Page 2


Chapter 4. The Language of Chemistry
Exercise 4
Solution 1.
Solution 2.
Solution 3.
 
(d) This equation satisfies the “Law of Conservation of Mass.” 
Law of Conservation of mass: “Matter is neither created nor destroyed in course of a 
chemical reaction.”
Solution 4.
(a)
Zn + H
2
SO
4
 ? ZnSO
4
 + H
2
This equation conveys following information:
1. The actual result of chemical change.
2. The substances take part in a chemical reaction and substances formed as a result 
of reaction.
3. Here one molecule of zinc, one molecule ofSulphuric acid react to give one molecule 
of zinc sulphate and one molecule of Hydrogen.
4. Composition of respective molecules i.e. one molecule ofsulphuric acid contains two 
atoms of hydrogen, one atom of sulphur and four atoms of oxygen.
5. Relativemoleculer masses of different substances i.e. molecular mass of 
Zn= 65, H
2
SO
4
 (2+32+64) = 98 
ZnSO
4
 (65+32+64) = 161 
H
2
 = 2
6. 22.4 litres of hydrogen are formed at S.T.P.
(b)
Mg + 2HCl
2
 ? MgCl
2
 + H
2
This equation conveys following information:
1. Magnesium reacts with of Hydrochloric acid to form Magnesium chloride and 
Hydrogen gas.
2. 24g of Magnesium react with 2(1 + 35.5) = 73g of Hydrochloric acid to produce (24 
+ 71) i.e. 95g of Magnesium chloride
3. That Hydrogen produced out at S.T.P. is 22.4 liters.
Page 3


Chapter 4. The Language of Chemistry
Exercise 4
Solution 1.
Solution 2.
Solution 3.
 
(d) This equation satisfies the “Law of Conservation of Mass.” 
Law of Conservation of mass: “Matter is neither created nor destroyed in course of a 
chemical reaction.”
Solution 4.
(a)
Zn + H
2
SO
4
 ? ZnSO
4
 + H
2
This equation conveys following information:
1. The actual result of chemical change.
2. The substances take part in a chemical reaction and substances formed as a result 
of reaction.
3. Here one molecule of zinc, one molecule ofSulphuric acid react to give one molecule 
of zinc sulphate and one molecule of Hydrogen.
4. Composition of respective molecules i.e. one molecule ofsulphuric acid contains two 
atoms of hydrogen, one atom of sulphur and four atoms of oxygen.
5. Relativemoleculer masses of different substances i.e. molecular mass of 
Zn= 65, H
2
SO
4
 (2+32+64) = 98 
ZnSO
4
 (65+32+64) = 161 
H
2
 = 2
6. 22.4 litres of hydrogen are formed at S.T.P.
(b)
Mg + 2HCl
2
 ? MgCl
2
 + H
2
This equation conveys following information:
1. Magnesium reacts with of Hydrochloric acid to form Magnesium chloride and 
Hydrogen gas.
2. 24g of Magnesium react with 2(1 + 35.5) = 73g of Hydrochloric acid to produce (24 
+ 71) i.e. 95g of Magnesium chloride
3. That Hydrogen produced out at S.T.P. is 22.4 liters.
Solution 5.
(a) A poly-atomic ion is a charged ion composed of two or more atoms covalently 
bounded that can be carbonate (CO
3
2-) 
and sulphate (SO
4
2-
)
(b) The fundamental laws which are involved in every equation are:
1. A chemical equation consists of formulae of reactants connected by plus sign (+) 
and arrow ( ?) followed by the formulae of products connected by plus sign (+).
2. The sign of an arrow ( ?) is to read ‘to form’. It also shows the direction in which 
reaction is predominant.
Solution 6.
(a) two 
(b) six 
(c) three 
(d) four 
(e) (i) three (ii) five (iii) four (iv) two
Solution 7.
According to law of conservation of mass, “matter can neither be created nor be 
destroyed in a chemical reaction”. This is possible only, if total number of atoms on the 
reactants side is equals to total number of atoms on products side. Thus, a chemical 
reaction should be always balanced.
Let us consider an example, 
Fe + H
2
O ? Fe
3
O
4
 + H
2 
In this equation number of atoms on both sides is not the same, the equation is not 
balanced. 
The balanced form of this equation is given by, 
3Fe + 4H
2
O  ? Fe
3
O
4
 + 4H
2
Solution 8.
Page 4


Chapter 4. The Language of Chemistry
Exercise 4
Solution 1.
Solution 2.
Solution 3.
 
(d) This equation satisfies the “Law of Conservation of Mass.” 
Law of Conservation of mass: “Matter is neither created nor destroyed in course of a 
chemical reaction.”
Solution 4.
(a)
Zn + H
2
SO
4
 ? ZnSO
4
 + H
2
This equation conveys following information:
1. The actual result of chemical change.
2. The substances take part in a chemical reaction and substances formed as a result 
of reaction.
3. Here one molecule of zinc, one molecule ofSulphuric acid react to give one molecule 
of zinc sulphate and one molecule of Hydrogen.
4. Composition of respective molecules i.e. one molecule ofsulphuric acid contains two 
atoms of hydrogen, one atom of sulphur and four atoms of oxygen.
5. Relativemoleculer masses of different substances i.e. molecular mass of 
Zn= 65, H
2
SO
4
 (2+32+64) = 98 
ZnSO
4
 (65+32+64) = 161 
H
2
 = 2
6. 22.4 litres of hydrogen are formed at S.T.P.
(b)
Mg + 2HCl
2
 ? MgCl
2
 + H
2
This equation conveys following information:
1. Magnesium reacts with of Hydrochloric acid to form Magnesium chloride and 
Hydrogen gas.
2. 24g of Magnesium react with 2(1 + 35.5) = 73g of Hydrochloric acid to produce (24 
+ 71) i.e. 95g of Magnesium chloride
3. That Hydrogen produced out at S.T.P. is 22.4 liters.
Solution 5.
(a) A poly-atomic ion is a charged ion composed of two or more atoms covalently 
bounded that can be carbonate (CO
3
2-) 
and sulphate (SO
4
2-
)
(b) The fundamental laws which are involved in every equation are:
1. A chemical equation consists of formulae of reactants connected by plus sign (+) 
and arrow ( ?) followed by the formulae of products connected by plus sign (+).
2. The sign of an arrow ( ?) is to read ‘to form’. It also shows the direction in which 
reaction is predominant.
Solution 6.
(a) two 
(b) six 
(c) three 
(d) four 
(e) (i) three (ii) five (iii) four (iv) two
Solution 7.
According to law of conservation of mass, “matter can neither be created nor be 
destroyed in a chemical reaction”. This is possible only, if total number of atoms on the 
reactants side is equals to total number of atoms on products side. Thus, a chemical 
reaction should be always balanced.
Let us consider an example, 
Fe + H
2
O ? Fe
3
O
4
 + H
2 
In this equation number of atoms on both sides is not the same, the equation is not 
balanced. 
The balanced form of this equation is given by, 
3Fe + 4H
2
O  ? Fe
3
O
4
 + 4H
2
Solution 8.
Solution 9.
Page 5


Chapter 4. The Language of Chemistry
Exercise 4
Solution 1.
Solution 2.
Solution 3.
 
(d) This equation satisfies the “Law of Conservation of Mass.” 
Law of Conservation of mass: “Matter is neither created nor destroyed in course of a 
chemical reaction.”
Solution 4.
(a)
Zn + H
2
SO
4
 ? ZnSO
4
 + H
2
This equation conveys following information:
1. The actual result of chemical change.
2. The substances take part in a chemical reaction and substances formed as a result 
of reaction.
3. Here one molecule of zinc, one molecule ofSulphuric acid react to give one molecule 
of zinc sulphate and one molecule of Hydrogen.
4. Composition of respective molecules i.e. one molecule ofsulphuric acid contains two 
atoms of hydrogen, one atom of sulphur and four atoms of oxygen.
5. Relativemoleculer masses of different substances i.e. molecular mass of 
Zn= 65, H
2
SO
4
 (2+32+64) = 98 
ZnSO
4
 (65+32+64) = 161 
H
2
 = 2
6. 22.4 litres of hydrogen are formed at S.T.P.
(b)
Mg + 2HCl
2
 ? MgCl
2
 + H
2
This equation conveys following information:
1. Magnesium reacts with of Hydrochloric acid to form Magnesium chloride and 
Hydrogen gas.
2. 24g of Magnesium react with 2(1 + 35.5) = 73g of Hydrochloric acid to produce (24 
+ 71) i.e. 95g of Magnesium chloride
3. That Hydrogen produced out at S.T.P. is 22.4 liters.
Solution 5.
(a) A poly-atomic ion is a charged ion composed of two or more atoms covalently 
bounded that can be carbonate (CO
3
2-) 
and sulphate (SO
4
2-
)
(b) The fundamental laws which are involved in every equation are:
1. A chemical equation consists of formulae of reactants connected by plus sign (+) 
and arrow ( ?) followed by the formulae of products connected by plus sign (+).
2. The sign of an arrow ( ?) is to read ‘to form’. It also shows the direction in which 
reaction is predominant.
Solution 6.
(a) two 
(b) six 
(c) three 
(d) four 
(e) (i) three (ii) five (iii) four (iv) two
Solution 7.
According to law of conservation of mass, “matter can neither be created nor be 
destroyed in a chemical reaction”. This is possible only, if total number of atoms on the 
reactants side is equals to total number of atoms on products side. Thus, a chemical 
reaction should be always balanced.
Let us consider an example, 
Fe + H
2
O ? Fe
3
O
4
 + H
2 
In this equation number of atoms on both sides is not the same, the equation is not 
balanced. 
The balanced form of this equation is given by, 
3Fe + 4H
2
O  ? Fe
3
O
4
 + 4H
2
Solution 8.
Solution 9.
Solution 10.
(a) The atomic mass unit (amu) is defined as 1/12
th
 of the mass of an atom of carbon.
1 a.m.u. = 1.67 x 10
-24
 gm = 1.67 x 10
-27
 kg 
1 gm mass = 6.02 x 10
23
 a.m.u. and 1 kg mass = 6.02 x 10
26
 a.m.u. (b)
(i) The relative molecular mass of = CuSO
4
5H
2
O 
= 63.5 + 32 + (16 x 4) + 5 (2 + 16) 
= 159.5 + 90 = 249.5
(ii) The relative molecular mass of = (NH
4
)
2
CO
3
 = N
2
H
8
CO
3 
= 14 x 2 + 1 x 8 + 12 + 3 x 16 
= 28 + 8 + 12 + 48 = 96
(iii) The relative molecular mass of = (NH
2
)
2
CO = N
2
H
4
CO 
= 2 x 14 + 1 x 4 + 12 + 16 
= 28 + 4 + 12 + 16 = 60 
(iv) The relative molecular mass of = Mg
3
N
2
 = 3 x 24 + 2 x 14 = 72 + 28 = 100
Solution 11.