Chemical Reactions And Equations Textbook Exercises With Solutions

 INTEXT QUESTIONS

1. Why should a magnesium ribbon be cleaned before burning in air?

🔴 The magnesium ribbon forms an oxide layer on its surface when exposed to air. This oxide layer prevents magnesium ribbon from reacting. Therefore this oxide layer should be removed with the help of sand paper before burning for  proper combustion.

2. Write the balanced equation for the following chemical reactions.

(i) hydrogen+chlorine➡️Hydrogen chloride

( ii) Barium chloride+ Aluminium sulphate➡️ Barium sulphate +Aluminium chloride

( iii) Sodium+Water ➡️Sodium hydroxide+ hydrogen

🔴( i)H2 + Cl2➡️ 2HCl

    (ii)3BaCl2+Al2(SO4)3➡️3BaSO4+2AlCl3

    ( iii)2Na+2H2O➡️2NaOH+H2

3. Write a balanced chemical equation with state symbols for the following reactions.

(i ) Solutions of Barium chloride and Sodium sulphate in water react to give insoluble Barium sulphate and the solution of Sodium chloride.

🔴BaCl2(aq)+Na2SO4(aq)➡️BaSO4(s)+ 2NaCl(aq)

(ii ) Sodium hydroxide solution( in water )reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

🔴NaOH(aq)+HCl(l)➡️NaCl(aq)+H2O(l)

4. A solution of a substance 'X' is used for whitewashing.

( i) Name the substance 'X' and write its formula. 

( ii)Write the reaction of the substance 'X' named in (i) above with water.

🔴( i) The substance 'X' is quicklime (calcium oxide) and its formula is CaO.

( ii) CaO + H2O➡️ Ca(OH)2 + Heat

5. Why is the amount of gas collected in one of the test tubes in activity 1.7 double of the amount collected in the other ? Name this gas.

🔴 It is because water is formed when hydrogen and oxygen combine in the ratio of 2:1 by volume, the gas with double volume is hydrogen. Thus, on decomposition of water the volume of hydrogen formed is twice than that of Oxygen gas.

           Electric current                                           2H2O ----------------> 2H2 + O2

       H2 : O2

          2 : 1