8. Write symbolic representation for the following word equations and balance them:

(a) Calcium carbonate →Calcium oxide + Carbon dioxide

Ans – (a)CaCO3→CaO+CO2

(b)Carbon +Oxygen →Carbon dioxide

Ans – C+O2→CO2

(c)Calcium oxide + Water→Calcium hydroxide

Ans – CaO+H2O→Ca(OH)2

(d)Aluminium +Chlorine →Aluminium chloride

Ans – 2Al+3Cl2→AlCl3

(e)Iron + sulphur →Iron sulphide

Ans – Fe+S→FeS

(f)Sodium carbonate + Hydrochloric acid (dil.)→Sodium chloride +Water +Carbon dioxide

Ans – Na2CO3+2HCl→2NaCl+H2O+CO2

(g)Barium chloride +Sodium sulphate →Barium sulphate + Sodium chloride

Ans – BaCl2+Na2SO4→BaSO4+2NaCl

(h)Iron sulphide +Hydrochloric acid (dil)→Iron(II) chloride + Hydrogen sulphide

Ans – FeS+2HCl→FeCl2+H2S

(i)Calcium + Water→Calcium hydroxide

Ans – Ca+2H2O→Ca(OH)2 +H2

OBJECTIVE TYPE QUESTION

1.Fill in the blanks :

(a) The substances which undergo chemical change are called reactants .

(b) The substances formed as a result of a chemical reaction are called products .

(c)During a chemical reaction ,transfer of energy takes place .

(d)The basic condition necessary for a chemical reaction is close contact.

(e)In some chemical reactions,an insoluble solid is formed when two solutions are mixed .

2. Write ‘true’ or ‘false’ for the following statements:

(a) No new substance is formed during a chemical reaction. [false]

Ans - New substance is formed during a chemical reaction.

(b) Hydrogen sulphide has rotten egg smell. [true]

(c)When potassium iodide solution is added to lead acetate solution ,a red precipitate is formed .[false]

Ans - When potassium iodide solution is added to lead acetate solution ,a yellow precipitate is formed.

(d) A black residue is formed when sugar is heated . [true]​