ANSWER IN BRIEF

  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)

    • 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 antifreezing agent in the radiators of vehicles in cold countries as the mixture of water with alcohol lowers the freezing point of water.


  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 :





    [NOTE : There is no mention in the text book (GSEB) of what an enzyme is.]

  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. Write the names of the products of oxidation reaction of ethanol in presence of KMnO4 and chromium oxide.
    ANS: Oxidation of ethanol in presence of KMnO4 yields ethanoic acid and water whereas its oxidation in presence of chromium oxide yields ethanal and water.

  9. 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.


  10. Write addition reactions of formaldehyde and propanone.
    ANS: Formaldehyde and propanone show following addition reactions with HCN forming corresponding cyanohydrins.





  11. 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.

  12. Mention the types of artificial polymers giving examples.
    ANS: Following are the types of artificial polymers :

    1. Synthetic fibre : rayon, nylon, polyester.
    2. Plastic : polythene, PVC, bakelite, melamine.
    3. Synthetic Rubber : butadiene, neoprene.


  13. What is the difference between 'thermoplastic' and 'thermosetting plastic' ?
    ANS:

    • Polymers which become soft on heating and regain original shape on cooling are called 'thermoplastics'. for example : polythene, polyvinyl chloride (PVC), and polystyrene.
    • Polymers which do not soften on heating at high temperature are called 'thermosetting plastics'. If at all they soften then they do not regain their shape. for example : bakelite, melamine.


  14. 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.

  15. 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.

  16. Write a brief note on soap.
    ANS: Soaps are sodium or potassium salts of higher fatty acids like stearic or palmitic acid, etc. 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.

  17. Write a note on 'Production of Soap'.
    ANS:
    [NOTE : this is described as preparation of soap as Activity 5 in the text book (GSEB) under the title 'For information of students'. The process described there is actually laboratory preparation of soap and is far from (large scale) production of soap.
    However, since the question appears in the list of questions given at the end of the chapter, we write the following answer.].

    • Take 20 ml of vegetable oil in a beaker and add 20% aqueous solution of NaOH to it.
    • Heat the mixture and shake it constantly till the mixture becomes dense.
    • Add 5 to 10 g NaCl to it.
    • On cooling the mixture, insoluble soap comes to the upper part of the beaker.
    • It is taken out in a separate plate and allowed to dry.
    • We can add fragrant materials, antiseptic drugs, fillers or any other additive as per the requirement.
    • Soap is generally used in the form of a cake in daily life.

      [NOTE : While preparing the text book, the so-called experts have forgotten to realise that by taking 20 ml vegetable oil it is difficult to prepare even single cake of soap. I am referring to the sentence given on page 217 which reads : 'Take this in other vessel and prepare cakes'.]


  18. Write a note on Detergents.
    ANS:

    • 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.


  19. Distinguish between soap and detergent.
    ANS:




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  1. Explain with example : Reaction of nonmetals with chlorine.
    ANS: Nonmetals form chlorides with chlorine. These chlorides are either liquid or gas.



  2. Explain with example : Reaction of nonmetals with hydrogen.
    ANS: Nonmetals form covalent hydrides with hydrogen.



    Methane (CH4), hydrochloric acid (HCl), etc. are hydrides of nonmetals.

  3. Mention physical properties of hydrogen.
    ANS:

    • Hydrogen is the lightest gas.

    • It is twenty times lighter than air.

    • It is a colourless and odourless gas.

    • It is insoluble in water.

    • It is inflammable

    • It is nonpoisonous.



  4. Mention uses of hydrogen.
    ANS:

    • Hydrogen Welding : When an electric arc is passed through hydrogen, it splits into atoms which release large amount of heat when they recombine to form molecules. This heat is used to melt and join (weld) the metals.

    • In the manufacture of ammonia by Haber's process.

    • In the manufacture of methanol and hydrochloric acid.

    • Liquid hydrogen is used as a fuel in space shuttles.

    • In the manufacture of vegetable ghee.



  5. Mention physical properties of sulphur.
    ANS:

    • It is pale greenish-yellow or greyish-yellow powder.
    • It is odourless and tasteless.
    • It is insoluble in water.
    • It is soluble in organic solvents like carbon disulphide, toluene (methyl
      benzene), etc.
 

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