ORGANIC COMPOUNDS -II : BRIEF ANSWERS

ANSWER IN BRIEF

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1. Explain : Functional group.
   

   ANS:
   

   
   
   • An atom or a group of atoms responsible for the chemical reactions of an organic compound is known as 'Functional Group'.
     
   • Functional groups are responsible for the properties of an organic compound.
     
   • Functional group is a characteristic of an organic compound.
     
   • Examples :
     
     
     
     1. Alcohol (-OH)
        
     2. Aldehyde (-CHO)
        
     3. Ketone (>C=O)
        
     4. Organic acid (-COOH)
        
     5. Ester (-COOR, R is alkyl part)
        
     6. -X (halogen, X stands for any of Cl, Br, I, F).
        
     
     
   • Thus, CH₃CH₂OH (ethanol) is an alcohol and -OH group decides its properties.
     
   • All compounds having similar functional group have similar properties.
     

   
   



2. Write physical properties of ethyl alcohol.
   

   ANS:
   

   
   
   • Pure ethanol is colourless.
     
   • Its boiling point is 78°C.
     
   • It is miscible with water.
     
   • It is neutral.
     

   
   



3. Mention uses of ethyl alcohol.
   

   ANS:
   

   
   
   • As an antiseptic to clean wounds.
     
   • To sterilise syringes, gauze, etc.
     
   • In alcoholic drinks.
     
   • In preparation of rectified spirit (alcohol containing 5% water).
     
   • As an industrial solvent.
     
   • In preparation of lacquers, varnish and perfumes.
     

   
   



4. Write about the harmful effects of ethyl alcohol.
   

   ANS:
   

   
   
   • Person consuming alcohol becomes addict to it.
     
   • Eyesight weakens and the person may lose eyesight in the long run.
     
   • Ethyl alcohol damages liver and may cause death of the person.
     
   • To restrict consumption of ethyl alcohol, some poisonous substance like methanol or CuSO₄ is added to ethanol. This is called 'Denatured Ethyl Alcohol'.
     

   
   



5. Show that the H atom in the -COOH group has acidic nature.
   

   ANS:The H atom in the -COOH group has acidic nature. The following two reactions are the proof of this.
   
   When acetic acid reacts with a metal like sodium or potassium, hydrogen gas is evolved.
   
   
   
   Acetic acid reacts with an alkali to form the respective salt of acetic acid and water.
   
   
   



6. What is an enzyme ? Write three reactions involving different enzymes.
   

   ANS: An enzyme is a biochemical catalyst which breaks down complex organic molecules into simpler ones. Some reactions involving enzymes are :
   
   
   
   
   



7. Mention the difference between 'Denatured Alcohol' and 'Rectified Spirit'.
   

   ANS:
   

   
   
   • Ethyl alcohol containing 5% water is called 'rectified spirit'.
     
   • Ethyl alcohol containing some poisonous substance like methanol or copper sulphate in small amount is called 'denatured alcohol'.
     
   • The purpose of adding poisonous substance is to prevent people from consuming alcohol as its addiction is harmful in the long run.
     

   
   



8. Explain : Tollen's test.
   

   ANS:
   [NOTE : Though this question appears in the list of questions given at the end of the chapter in the text book (GSEB), the description regarding it is given under the title 'ONLY FOR INFORMATION'. Refer to 'Activity 4' in the text book.]
   

   
   
   • Add sufficient NaOH to a solution of silver nitrate to obtain permanent precipitates.
     
   • Dissolve the precipitates in NH₄OH to prepare Tollen's reagent.
     
   • Add some aldehyde in the test tube containing Tollen's reagent and place it in a beaker containing water.
     
   • Heat the water in the beaker.
     
   • The aldehyde will be oxidised and silver (Ag) metal will be liberated. This silver will appear as a mirror on the inner wall of the test tube.
     

   
   



9. Write addition reactions of formaldehyde and propanone.
   

   ANS: Formaldehyde and propanone show following addition reactions with HCN forming corresponding cyanohydrins.
   
   
   
   
   



10. What is a polymer ? Give its classification.
    

    ANS: A polymer is a long-chain compound with many smaller units called monomers.
    
    Based on their reactions, polymers are classified into (i) Addition polymer and (ii) Condensation polymer.
    



11. What are addition polymers ? Give examples.
    

    ANS: Addition polymers are formed by addition of one or more than one (same or different) unsaturated monomer having double or triple bond.
    
    Polythene, PVC, TEFLON, polypropene, natural rubber, polubutadiene and neoprene are addition polymers.
    



12. What are condensation polymers ? Give examples.
    

    ANS: A polymer formed by the condensation of two or more than two monomers with the elimination of a simple molecule like water or ammonia is called a condensation polymer.
    
    Polyester, polyamides and phenol-formaldehyde are condensation polymers.
    



13. Write a brief note on soap.
    

    ANS: Soaps are sodium or potassium salts of higher fatty acids like stearic or palmitic acid, etc. Soap is in the form of acid, its glycol and ester compounds. The ester compounds are glycerides present in animal fat or vegetable oils. In soaps, -COONa is the functional group attached to the hydrocarbon part.
    
    PREPARATION : On heating vegetable oil or animal fat (esters of higher fatty acids) with sodium hydroxide, sodium salt of fatty acid (soap) and glycerol are formed.
    
    
    
    This process is known as Saponification.
    



14. Write a note on (Synthetic) Detergents.
    

    ANS:
    

    
    
    • (Synthetic) Detergents are sodium salts of long-chain sulphonates.
      
    • In detergents, -SO₃Na is the functional group attached to hydrocarbon part.
      
    • Detergents are superior to soaps as soaps cannot be used with hard water. Soaps form insoluble salts of calcium and magnesium in hard water and cleansing becomes difficult because of Ca⁺² and Mg⁺² ions present in hard water.
      
    • Detergents do not form precipitates with these ions. Due to this detergent is used in lesser quantity and its cleansing effect is retained.
      

    
    



15. Distinguish between soap and detergent.
    
    ANS:
    
    
    


16. 
    

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