A dry pellet of a common base B when kept in open absorbs moisture and turns sticky. The compound is also a by-product of the chlor-alkali process.  

Schematic-diagram-of-chlor-alkali-process - Teachoo.png


(a) Identify B:  

(i) Sodium chloride 

(ii) Sodium hydroxide  

(iii) Carbon dioxide 

(iv) Sodium carbonate  


Given that

Common base Base B , when kept in open, absorbs moisture


  • Chlor-Alkali process is a method for the industrial production of sodium hydroxide and chlorine by the electrolysis of sodium chloride solution.  
  • Since B is a base, it cannot be sodium chloride because it is a salt.
    Therefore, B is sodium hydroxide (NaOH)

    So, the correct option is (ii) Sodium hydroxide

(b) What type of reaction occurs when B is treated  with an acidic oxide?  

(i) Neutralisation  

(ii) Double decomposition  

(iii) Combination  

(iv) Displacement  




  • Neutralisation reaction : In this, acid and base react with each other to form salt and water.
  • Double decomposition reaction: it is a reaction between two compounds in which each are interchanged to form two new compounds i.e. AB+CD→AC+BD
  • Displacement Reaction: Reaction in which more reactive element takes the place of less reactive element.
  • Combination Reaction: When two or more substances react to form a single product, it is known as combination reaction i.e. A+B→C+D

    Since B is Sodium Hydroxide i.e a base , when we react it with an acidic oxide , neutralization reaction will take place.

    So, the correct answer is (i) 

(c) What is the raw material used in chloro-alkali?  

(i) aqueous solution of sodium chloride  

(ii) sodium chloride in dry form  

(iii) sodium hydroxide  

(iv) sodium carbonate  



  • The raw material used in the chlor-alkali process is aqueous solution of sodium chloride , also known as brine .
  • We use aqueous NaCl and not dry NaCl because in presence of water, NaCl dissociates to produce Na + and Cl - ions which conduct electricity.

    So, the correct answer is (i) 


(d) When aqueous sodium carbonate (Na 2 CO 3 ) reacts  with HCl (aq), it gives  

(i) NaOH, H 2 and CO 2   

(ii) NaCl, H 2 O and CO 2   

(iii) NaHCO 3 , H 2 and CO 2   

(iv) NaHCO 3 , H 2 O and CO 2



Sodium carbonate is basic in nature. So, when it reacts with HCl (acid), a neutralisation reaction takes place and salt, water and CO 2 is produced.

The reaction is as follows: 

Na 2 CO 3 (aq) + 2HCl(aq) → 2NaCl + H 2 O + CO 2

Sodium Carbonate reaction with HCl (aq) - Teachoo-01.jpg


Therefore, the correct answer is (ii) NaCl, H 2 O and CO 2  

  1. Class 10
  2. Chapter 2 Class 10 - Acids, Bases and Salts (Term 1)

About the Author

CA Maninder Singh's photo - Founder at Teachoo
CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo