Solution of CARBON AND ITS COMPOUND

1. What do you mean by organic chemistry?
Ans.The chemistry dealing with organic compound which are derived from living organisms is called organic chemistry.  

2. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Ans. The two characteristic features seen in carbon, that is, tetravalency and catenation, put together give rise to a large number of compounds. 

3. Why carbon generally form compounds by covalent bond.
Ans.  Carbon has four electrons in its outermost shell and needs to gain or lose four electrons to attain noble gas configuration.so carbon generally form compounds by covalent bond.

4. The covalent bonds that carbon forms with most other elements are very strong. Why?

 Ans.It is because the formation of strong bonds by carbon atoms due to its small size.This enables the nucleus to hold on to the shared pairs of electrons strongly. The bonds formed by elements having larger atoms are much weaker.

5. Name the reaction that is commonly used in the conversion of vegetable oil to fats. 
Ans. Hydrogenation reaction is commonly used in the conversion of vegetable oil to fats. 

6. Write the  structural formula of the following compounds benzene and hexane.state the number of double bonds in benzene.
Ans.  Structural formula of the hexane - CH₃ -CH₂ -CH₂ -CH₂ - CH₂-CH₃ 
Structural formula of the  benzene=

Number of double bond is 3.

7. Write the structure of Buckminsterfullerene.
Ans. Structure of fullerenes is C-60 which has carbon atoms arranged in the shape of a football. 

8. What Is an homologous series ?
Ans. A group of organic compound having a similar structure and similar chemical properties in which the successive compound differ by a CH₂ group.

Ex. CH₄  C₂H₆  C₃CH₈   ..... 

9. Write the name of the following compounds:  CH₃CH₂COOH, C₆H₆ .C₆H₁₄

Ans. CH₃CH₂COOH - Propanoic acid.
 C₆H₆. - Benzene.
 C₆H_14.  - Hexane. 

10. Name the homologous series to which  C₁₀H₁₈ and B is C₁₈H₃₆  are belong. 
Ans. They belongs to alkyne group -C_nH_2n-2.   _{( n=10 ,  2n-2 = 20 - 2=18)}        

11. Write the name of the following compounds:
(i) HCOOH,   (ii) CH₃COCH₂CH_3.
Ans.  (i) HCOOH - Formic acid
(ii) CH₃COCH₂CH_3.. - Butanone.

12. Complete the reaction. CH₃COOH + NaHCO₃→?
Ans.  CH₃COOH + NaHCO₃→ CH₃COONa + CO₂+ H₂O

13. What are the allotropes of carbon?
Ans. There are three forms of carbon called allotropes of carbon - Diamond, Graphite and Buckminsterfullerene.
They have same chemical properties but difference in physical properties due to their different structure. 

14. Are structural isomers possible for bromopentane? 
Ans. Yes. many structural isomers are possible for bromopentane because bromine atom can be atached to any of the carbons of pentane.

15. Why coal and petroleum are called fossil fuels?
Ans. Coal and petroleum are called fossil fuels because coal and petroleum are formed from remains of trees, tiny plants and animals that lives million of years ago. 

16. What are oxidising agents?
Ans. Oxidising agents are the substances provides oxygen or can gain elctrons during reaction.

17. What is the cause of hardness of water? 
Or 
How can you convert distil water into hard water?
Ans.By dissolving hydrogen carbonates/ sulphates /chlorides of calcium or magnesium in water we can convert distil water into hard water.

18. Name the following compound.
       H       H       H        H      H        
     丨    丨     丨    丨     丨   
H— C — C —  C — C —  C ☰ C — H
     丨    丨     丨    丨     丨   
       H        H      H        H       H        
Ans. Hex -one-yne

19. What is vinegar? Give its uses.
Ans. Ethanoic acid is commonly called acetic acid and belongs to a group of acids called carboxylic acids and it is called vinegar. Carboxylic acids is widely used as a preservative in pickles.

20. Explain why carbon generally form compounds by covalent bond. 
Or
State the reason why carbon can neither form C⁴⁺ cations nor C^4-  anion but forms covalent compound
Ans.  Carbon has four electrons in its outermost shell and needs to gain or lose four electrons to attain noble gas configuration and formed C^4- anion  and   C⁴⁺ cation. To gain four electrons or to lose 4 electrons, it would require a large amount of energy.Carbon overcomes this problem by sharing its four valence electrons with other atoms of carbon or with atoms of other elements so carbon generally form compounds by covalent bond. 

21. Why are covalent compounds generally poor conductors of electricity?
Ans. Covalent compounds generally poor conductors of electricity because 
i. The forces of attraction between these molecules are not very strong.
ii. The bonding in these compounds does not give rise to any ions. 

22. Define vital force theory.
Ans. Compounds were initially extracted from natural substances and it was thought that these carbon compounds or organic compounds could only be formed within a living system and they are the product of some ' vital force'of nature.This is called vital force of theory.

23.Write the general formula of alkane, alkene and alkyne.
Ans. General formula of Alkanes - CnH_2n+2.
       General formula of Alkanes - CnH_2n

       General formula of Alkanes - CnH_{2n - 2}

24. How many structural isomers can you draw for pentane?
Ans. The hydro carbons which contain carbon atom more than 4, can exhibit the property of isomerism and propane has three carbon atoms so propane cannot exhibit structural isomers. 

25.What are hydrocarbons? 
Ans. All these carbon compounds which contain just carbon and hydrogen are called hydrocarbons. Among these, the saturated hydrocarbons are called alkanes. The unsaturated hydrocarbons which contain one or more double bonds are called alkenes. Those containing one or more triple bonds are called alkynes.

26. What Is an homologous series ? 
Ans. A series of compounds in which the same structure and same functional group substitutes for hydrogen in a carbon chain,is called a homologous series. In homologous series successive compounds differ by CH₂ and having different chemical properties.
Ex. Methane - CH₄  Ethane - C₂H₆ , Propane - C ₃ H ₈, Butane -C₄ H₁₀.., ,  etc.

27. What are hetero atoms?
Ans. Carbon also forms bonds with other elements such as halogens, oxygen, nitrogen and sulphur. In a hydrocarbon chain, one or more hydrogen can be replaced by these elements, such that the valency of carbon remains satisfied. In such compounds, the element replacing hydrogen is referred to as a heteroatoms.

28. (i) Calculate the difference in the formulae and molecular masses for
(a) CH₃ OH and C₂H₅ OH (b) C₂H₅ OH and C₃H ₇ OH, and (c) C₃H ₇ OH and C₄H ₉ OH.
(ii) Is there any similarity in these three? 
(iii) Arrange these alcohols in the order of increasing carbon atoms to get a family. Can we call this family a homologous series? 
(iv) Generate the homologous series for compounds containing up to four carbons for the other functional group.
Ans. (i) Difference in the formulae - CH₂. Difference in the molecular masses -14
(ii) Yes, all have same functional group OH
(iii) CH₃OH, C₂H₅ OH, C₃H ₇ OH and C₄H₉OH. Yes we call this family a homologous series due to presence of same functional group.
(iv) CH₃Cl, C₂H₅ Cl, C₃H ₇ Cl and C₄H₉OH

29. What is an alkyl group?                      
Ans. The alkyl group is a type of functional group that contain  carbon and hydrogen atom present in its structure. The general formula for an alkyl group is C_nH_2n+1,          

30. Saturated hydrocarbons will generally give a clean flame while unsaturated carbon compounds will give a yellow flame with lots of black smoke sooty flame.Why?
Ans. Unsaturated hydrocarbons contain a greater proportion of carbon than saturated hydrocarbon, so all the carbon particles do not get oxidised.Due to incomplete combustion unsaturated carbon compound give sooty flame and saturated hydrocarbons give clean flame due to complete combustion.

31. Why do substances burn with or without a flame?
Ans. This is because a flame is only produced when gaseous substances burn. When wood or charcoal is ignited, the volatile substances present vapourise and burn with a flame in the beginning and after some time burn without flame due to absence of volatile or gaseous substances. 

32. How would you name the following compounds?
(i) CH₃ - CH₂Br  (ii) CH₃ -CH₂ - CH₂ - C ☰ C - H  (iii)H-CHO
Ans. (i) (i) CH₃ - CH₂Br - Bromoethane.
(ii) CH₃ -CH₂ - CH₂ - C ☰ C - H - Pent-one-yne. 
(iii) HCHO - Methanal  or Formaldehyde. 

33. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?

Ans. When ethanol react with oxidising agent potassium dichromate or potassium permanganate, it oxidised into ethanoic acid by adding oxygen, so it is called oxidation reaction.

34.Name the reaction which is commonly used in the conversion of vegetable oil or fats. Explain the reaction involved in detail.

Ans. Hydrogenation reaction which is commonly used in the conversion of vegetable oil into vanaspati ghee. In this process hydrogen and vegetable oil are passed over catalyst such as palladium or nickel at 200 degree celsius. 

35. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?

Ans. Ethyne burns in oxygen to give carbon dioxide along with the release of large amount of heat and light so it is used for welding. But a mixture of ethyne and air is not used because air contains other gases due to which it may produces sooty flame and less amount of heat.

36. What is denatured alcohol or methylated spirit?
Ans. To prevent the misuse of ethanol produced for industrial use, it is made unfit for drinking by adding poisonous substances like methanol to it. Dyes are also added to colour the alcohol blue so that it can be identified easily. This is called denatured alcohol.

37. Write the uses of alcohol as a fuel.
Ans.  Sugarcane juice can be used to prepare molasses which is fermented to give alcohol (ethanol). Some countries now use alcohol as an additive in petrol since it is a cleaner fuel which gives rise to only carbon dioxide and water on burning in sufficient air (oxygen).

38.  Write the properties of Ethanoic Acid.
Ans.  (i) Ethanoic acid is commonly called acetic acid and belongs to a group of acids called carboxylic acids and it is called vinegar. 
(ii) The melting point of pure ethanoic acid is 290 K.
(iii) It is acidic in nature and it is a weak acid.

39. Why acetic acid is called glacial acetic acid?
 Ans. The melting point of pure ethanoic acid is 290 K (17 C^o) and hence it often freezes during winter in cold climates. This gave rise to its name glacial acetic acid.

40.Why carboxylic acids are weak acids?
Ans. Carboxylic acids are obviously characterised by a special acidity. However, unlike mineral acids like HCl, which are completely ionised, carboxylic acids are not completely ionised in water so it is a weak acids.

41. Take two test tubes with about 10 mL of hard water in each.  Add five drops of soap solution to one and five drops of detergent solution to the other.  Shake both test tubes for the same period. 
(i) Do both test tubes have the same amount of foam? „ 
(ii) In which test tube is a curdy solid formed?
Ans. (i) No.
(ii)  Test tubes with about 10 mL of hard water and detergent solution because detergent can form lather in hard water while soap cannot. 

42.Write the formula and draw electron dot structure of carbon tetrachloride.
Ans. The formula of carbon tetra-chloride is - CCl₄
 Dot structure of carbon tetra-chloride             Cl
                                                                    ∶
                                                             Cl .. C  .. Cl 
                                                                     ∶              
                                                                    Cl
43. Draw the electron-dot structure structural formula of 
(i) Nitrogen molecule.(ii) Ethyne.
Ans.(i) Electron dot structure of Nitrogen molecules -  ・N ⋮⋮ N・
(ii) Ethyne.                                                           -  H։ C ⋮⋮⋮ C ։

44. (a) What is the difference in the molecular mass of any two adjacent homologouses?
(b) What is the difference in the molecular formula of any two adjacent homologouses?

(c) Which of the following belong to the same homologous?
C₃H₈, C₄H₈, C₄H₆, C₃H₆.
Ans.(a) The difference in the molecular mass of any two adjacent homologouses- 14 
(b) The difference in the molecular formula of any two adjacent homologouses- CH₂
(c) C₃H₆ and C₄H₈.are belongs to the same homologous.

45. Complete the following reaction:
(i) CH₄ + Cl₂^sunlight→ ......+ HCl 
(ii) CH₃CH₂OH ^{conc.sulphuric acid}→.....+ H2O.
Ans.( i) CH₄ + Cl₂^sunlight→  CCl₄+ HCl. (substitution reaction).

(ii) CH₃CH₂OH ^{conc.sulphuric acid}→C₂H₄+ H₂O.

46. How is scum formed?

Ans.When a soap is used for bathing or washing cloths in hard water, foam is formed with difficulty and an insoluble substance  remains after washing with water. This insoluble substance is called scum. This is because charged calcium and magnesium particles present in the hard water react with soap to form an insoluble substance.

47. (i) Name the products formed when ethanol burns in air. ‘
(ii) What two forms of energy are liberated on burning alcohol?
How an addition reaction is useful in vegetable ghee industry?

Ans. (i) When ethanol burns in air, carbon-dioxide and water vapour formed.

(ii) Two forms of energy are heat and light liberated on burning alcohol . 

48. What happens when a small piece of sodium is dropped into ethanol? 
Or. 
Write the reaction between sodium and ethanol or alcohol.
Ans. When ethanol react with sodium at room temperature, hydrogen is evolved with formation of sodium ethoxide.
C₂H₅OH  + Na ➝   C₂H₅ONa + H₂  

Ethanol               Sod.          Sod-ethoxide          Hydrogen gas    
                    
49.How would you distinguish experimentally between an alcohol and a carboxylic acid? 
Ans. Alcohol does not react with carbonate or bicarbonate, it react with sodium and produce sodium ethoxide and hydrogen gas. 

Carboxylic acid react with carbonate and bicarbonate and produce sodium ethanoate, carbon dioxide and water.

50. Define esterification reaction. What are esters? 
Ans. Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to give an ester' This reaction is called esterification.
  CH₃COOH + C₂H₅OH = CH₃COOC₂H₅ + H₂O
 Ethanoic acid     Ethanol            ester                   Water

Esters are sweet-smelling substances. These are used in making perfumes and as flavouring agents.

51.  Why soap do not form lather in hard water? 
Or
Mention the disadvantages of the cleaning clothes with soap in hard water.

Ans. In the reaction of soap with the calcium and magnesium salts, which cause the hardness of water, an insoluble substance (scum) is formed due to soap do not form lather in hard water.

52. An organic compound A of molecular formula C₂H₆O on oxidation with dilute alkaline  solution gives an acid B with the same number of carbon atoms. Compound A is often used for sterilization of skin by doctors.
(i) Name the compounds A & B.
(ii) Write a chemical equation involved in the formation of B from A.
Ans. (i) The compounds A & B are ethanol and ethanoic acid.
(ii) Chemical equation involved in the formation of B from A :
                   KMNO₄

C₂H₅OH ——➝ CH₃COOH

 Ethanal              Ethanoic acid

53. A salt X is formed and a gas is evolved when ethanoic acid reacts with sodium hydrogen carbonate. Name the salt X and the gas evolved. Also write the chemical equations of the reaction involved.
Ans. X is sodium ethoxide formed and a gas carbondioxide is evolved when ethanoic acid reacts with sodium hydrogen carbonate.
CH₃COOH + NaHCO₃→ CH₃COONa + H₂O + CO₂.

54. What is a catalyst? Write the chemical equation to represent the hydrogenation of ethene.
Ans.  Catalysts are substances that cause a reaction to occur or proceed at a different rate without the reaction itself being affected.

The chemical equation to represent the hydrogenation of ethene - 

                  Nickel catalyst

CH₂=CH₂   ---------------→ CH₃ - CH₃ 

55.Name oxidizing agent used for the conversion of ethanol and to ethanoic acid. Distinguish between ethanol and ethanoic acid on the basis of

(i) litmus test (ii) reaction with sodium carbonate.

Ans. Alkaline potassium permangnate or acidified potassium chromate.

(i) Ethanol is neutral in nature so no change in litmus test. Ethanoic acid changes blue litmus into red.

(ii) Ethanol does not react with sodium carbonate, it react with sodium and gives sodium ethoxide.

Ethanoic acid react with sodium carbonate and gives sodium acetate salt.

56. Why is the reaction between methane and chlorine considered as a substitution reaction? 

 Ans. In the presence of sunlight, chlorine is added to hydrocarbons methane  in a very fast reaction. Chlorine can replace the hydrogen atoms from methane one by one. In this reaction one type of atom or a group of atoms takes the place of another, so it is called a substitution reaction. 

57. Explain tetra valency and catenation.Name an element other than carbon which exhibit the property of catenation upon 7 or 8 atoms. 

Ans.Tetra valency- Since carbon has a valency of four, it is capable of bonding with four other atoms of carbon or atoms of some other mono-valent elements. This property is called tetravalency. 

 Catenation- Carbon has the unique ability to form covalent bonds in order to straight chain, branched chain and cyclic chain, with other atoms of carbon, giving rise to large molecules. This property is called catenation.
Si and S exhibit the property of catenation.

58. Both diamond and graphite are formed by carbon atoms, but they have different physical properties. Why?
And. Both diamond and graphite are formed by carbon atoms, the difference lies in the manner in which the carbon atoms are bonded to one another. 
In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure. 
In graphite, each carbon atom is bonded to three other carbon atoms in the same plane giving a hexagonal array. One of these bonds is a double-bond, and thus the valency of carbon is satisfied. Graphite structure is formed by the hexagonal arrays being placed in layers one above the other.
These two different structures result in diamond and graphite having very different physical properties even though their chemical properties are the same. 
Diamond is the hardest substance known while graphite is smooth and slippery. Graphite is also a very good conductor of electricity unlike other non-metals 

59. List two differences between saturated and unsaturated hydrocarbons. 
Ans. Saturated hydrocarbons -The carbon compound whose valencies of all the atoms are satisfied by single bonds between them are called saturated compounds. These compounds are normally not very reactive.
Ex - Methane (CH₄), Ethane (C₂H₆)

Unsaturated hydrocarbons -The carbon compound whose valencies of the atoms are satisfied by double bonds or triple bond between them, are known as unsaturated carbon compounds and they are more reactive than the saturated carbon compounds.
Ex - Ethene (C₂H₄), Propene (C₃H₆).

60. Define functional group?
Ans.  In a hydrocarbon chain, one or more hydrogen can be replaced by a group of atoms like  halogens, oxygen, nitrogen and sulphur which confers  specific properties to the compound called functional group.           
Example=  F, Cl, Br, I, 
 Alcohol  —OH   
Aldehyde - CHO ,        O
                                 ll
Ketone   -                 -C - 

Carboxylic acid        -COOH, 

61. What is the relation between the number of carbon and hydrogen atoms in the compounds of homologous series? 
Ans. As the number of carbon and hydrogen atoms or molecular  in the compounds of homologous series increases, mass increases in any homologous series, a gradation in physical properties is seen. This is because the melting points and boiling points increase with increasing molecular mass. 
Other physical properties such as solubility in a particular solvent also show a similar gradation. But the chemical properties, which are determined solely by the functional group, remain similar in a homologous series.

62. What will be the formula and electron dot structure of cyclopentane?
Ans. The formula of cyclopentane - C₅H₁₀                 
                                                                                   H•         •H
 Dot structure of cyclopentane -                  • C •
                                                                •     •
                                                   H ••   •            •  •• H
                                                          C                C
                                                  H ••   •              •   •• H
                                                             •          •
                                                         H•• C •• C •• H
                                                               •     •
                                                               •     •
                                                               H    H

63. Draw the structures for the following compounds.
 (i) Ethanoic acid (ii) Bromopentane* (iii) Butanone (iv) Hexanal (v) Chloroethane.
Ans.  (i) Ethanoic acid CH3COOH -
                                H   O                       
                             l    ll                       
                       H - C - C - OH          
                             l                              
                            H 
(ii) Bromopentane*
                                   CH₃  -CH₂  -  CH₂  -  CH₂  -  CH₂Br 

(iii) Chloroethane.  CH₃ -CH₂Cl 
                                           
(iii) Butanone -    CH₃ - CH₂ - C- CH₃
                                            ll
                                                             O


64. How coal and petroleum formed?
Ans. Coal and petroleum have been formed from biomass which has been subjected to various biological and geological processes. Coal is the remains of trees, ferns, and other plants that lived millions of years ago. These were crushed into the earth, perhaps by earthquakes or volcanic eruptions. They were pressed down by layers of earth and rock. They slowly decayed into coal.
 Oil and gas are the remains of millions of tiny plants and animals that lived in the sea. When they died, their bodies sank to the sea bed and were covered by silt. Bacteria attacked the dead remains, turning them into oil and gas under the high pressures they were being subjected to. 

65. (i) Name the products formed when ethanol burns in air.

(ii) Name the products formed when oxidised in the presence of potassium dichromate or potassium per magnet.
Or.
Write the chemical equations for the conversion of ethanol to it ethanoic acid in the presence of K₂Cr₂O₇  or KMnO₄  .

Ans. (i) When ethanol burns in air,carbon dioxide and water are formed.
C2H5 +O2————➝CO₂ + H₂O'  

(ii) When ethanol react with potassium dichromate or potassium per magnet(oxidising agent) during oxidation, it first converted into aldehyde and later change into acetic acid ( Ethanoic acid). Oxidising agent provides nascent oxygen for oxidation.

              (o)           

C₂H₅OH ————➝ CH₃CHO + H₂O ————➝ CH₃COOH

              K2Cr₂O₇     Ethanal                            Ethanoic acid

66. Define addition and substitution reaction.

Ans. Addition reaction- Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons. This phenomenon is called addition reaction.

                         C₂H₄ + H₂ = C₂H₆ 

                                            Ethene                  Ethane

 This reaction is commonly used in the hydrogenation of vegetable oils.

Substitution reaction - Saturated hydrocarbons are fairly unreactive and are inert in the presence of most reagents. However, in the presence of sunlight, chlorine is added to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen atoms one by one. It is called a substitution reaction.

CH₄ + Cl₂ = CH₃Cl + HCl 

(in the presence of sunlight)

67. Write the properties of ethanol.
Ans. (a) Ethanol is a liquid at room temperature
(b) Inflammable volatile liquid
(c) Soluble in water in all proportions.
(d) Colourless and have a faint odour.
(e) Intake of even a small quantity of pure ethanol (called absolute alcohol) can be lethal. Also, long-term consumption of alcohol leads to many health problems.

68.(i) Name the carbon compound which on heating with excess of sulphuric acid at 443 K gives ethene.Give its equation. State the role of conc. H₂SO₄, in this reaction. Write the chemical equation for this reaction Or Why sulphuric acid is regarded as hydrating agent in this reaction?
Ans. Compound is ethanol which on heating with excess of sulphuric acid at 443 K gives ethene.
               conc. H₂SO₄ 
C₂H₅OH    ------------➝  CH₂= CH₂ +  H₂O
                              170^o
(ii) In this reaction ethanol reduced to ethyne. Concentrated sulphuric acid regarded as a dehydrating agent in this reaction because it removes water from ethanol.  

69. How do alcohols affect living beings?
Ans. When large quantities of ethanol are consumed, it tends to slow metabolic processes and to depress the central nervous system. This results in lack of coordination, mental confusion, drowsiness, lowering of the normal inhibitions, and finally stupor. The individual may feel relaxed but does not realise that his sense of judgement. Unlike ethanol, intake of methanol in very small quantities can cause death.

70. What is meant by saponification? Give an example.
Ans. Esters react in the presence of an acid or a base to give back the alcohol and carboxylic acid. This reaction is known as saponification because it is used in the preparation of soap.
                          NaOH 
 CH₃COOC₂H₅ ------------➝CH₃COOH + C₂H₅OH
CH₃COOH + NaOH ------------➝ CH₃COONa + H₂O
                                            Sodium ethanoate   Water
                                                 or Sod.acetate
71. Name the products formed when ethanoic acid(C₂H₄O₂)reacts with sodium hydrogen carbonate(NaHCO₃) and sodium carbonate.How would you prove the presence of this gas?
Or
 How does ethanoic acid react with carbonates and hydrogen carbonates?
Ans. Ethanoic acid reacts with carbonates and hydrogen carbonates to give rise to a salt, carbon dioxide and water. The salt produced is commonly called sodium acetate. 
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂ 
CH₃COOH + NaHCO₃→ CH₃COONa + H₂O + CO₂
We can prove the presence of carbon dioxide gas by passing this gas through lime water. If lime water turns into milky, the gas is carbon dioxide.
72. Explain the effect of soap in cleaning.
Ans. The effect of soap in cleaning -  Most dirt is oily in nature and oil does not dissolve in water. The molecules of soap are sodium or potassium salts of long-chain carboxylic acids. The ionic-end of soap dissolves in water while the carbon chain dissolves in oil. The soap molecules, thus form structures called micelles where one end of the molecules is towards the oil droplet while the ionic-end faces outside. This forms an emulsion in water. The soap micelle thus helps in dissolving the dirt in water and we can wash our clothes clean.

73. What is micelle ?
Ans. Soaps are molecules in which the two ends have differing properties, one is hydrophilic, that is, it dissolves in water, while the other end is hydrophobic, that is, it dissolves in hydrocarbons. When soap is at the surface of water, the hydrophobic ‘tail’ of soap will not be soluble in water and the soap will align along the surface of water with the ionic end in water and the hydrocarbon ‘tail’ protruding out of water. Inside water,these molecules have a unique orientation that keeps the hydrocarbon portion out of the water.This is achieved by forming clusters of molecules in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. This formation is called a micelle. 

74. Draw the structure for the following compounds:
(i) 2- Bromopentane
(ii) 2-methyl propane
(iii) Butanol
(iv) 1-Hexyne.                                         
Ans. (i) The structure of 2- Bromopentane 
        H   H    H   H   H
         l    l     l    l     l   
   H - C - C - C - C - C - H
         l    l     l    l     l
        H   H   H   Br   H
(ii) 2-methyl propane - 
         H    H     H   
          l     l      l       
   H - C  - C -  C - H 
         l     l      l    
        H H-C-H  H
                 l             
                H                           
(iii) Structure of butanol-    
     H  H    H   H
      l    l     l     l
H- C - C - C - C- OH
      l     l    l     l
     H    H   H   H 

75. An organic compound A is widely used as a preservative in pickles and has a molecular formula C₂H₄O₂. The compound reacts with ethanol in presence of an acid to form a sweet-smelling compound B.(i) Identify the compound.
(ii) Write the chemical equations for its the reaction with ethanol to form compound B.
(iii) How can you get A back from B.
(iv) Name the process and write the corresponding chemical equation.
Ans. (i) Compound is Esters.
(ii) CH₃COOH + C₂H₅OH➝ CH₃COOC₂H₅ + H₂O in the presence of acid.
     Ethanoic acid             Ethanol                  Ester                       Water
(iii) When esters react in the presence of an acid or a base to give back the alcohol and carboxylic acid.
(iv) This process is known as saponification because it is used in the preparation of soap.
                    NaOH 
CH₃COOC₂H₅. ➝   CH₃COOH + C₂H₅OH.
Ester             Ethanoic acid           Eethanol

76.Write balanced chemical equation for the following:
(i)  Methane is burned in insufficient air.
(ii) Ethanol is treated with sodium
(iii) Ethanoic acid is react with is sodium hydroxide
(iv) Ethanoic acid is treated with sodium carbonate.
(v) Ethanol is mixed with ethanoic acid in the presence of an acid.
Ans. (i) When methane is burned in insufficient air it produces large amount of heat, carbon-dioxide and water vapour.
CH₄ + O₂ → CO₂ + H₂O + heat and light.
(ii) When ethanol is treated with sodium it produces sodium ethoxide and hydrogen gas.
 2Na + 2CH₃-CH₂OH → 2CH₃-CH₂ONa+ + H₂
(Sodium)  (Eethanol)          (Sodium ethoxide)    (Hydrogen)
(iii)Ethanoic acid is react with is sodium hydroxide.
 Like mineral acids, ethanoic acid reacts with sodium hydroxide to give a salt sodium ethanoate and water:
 NaOH + CH₃COOH → CH₃COONa + H₂O
(iv) When ethanoic acid is treated with sodium carbonate- 
 Ethanoic acid reacts with carbonates and hydrogen carbonates to give rise to a salt, carbon dioxide and water. The salt produced is commonly called sodium acetate. 
2CH₃COOH + Na₂CO3 → 2CH₃COONa + H₂O + CO₂ 
CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂ 
(v) Ethanol is mixed with ethanoic acid in the presence of an acid.
 CH₃COOH + C₂H₅OH➝ CH₃COOC₂H₅ + H₂O in the presence of acid.
  Ethanoic acid             Ethanol                  Ester                       Water

77. An organic compound X on heating with conc. H₂SO₄ forms a compound Y which on addition of one molecule of hydrogen in the presence of nickel forms a compound Z. One molecule of compounds Z on combustion form two molecules of CO₂ and three molecules of H₂O. Identify giving reasons that compounds X , Y and Z. Write the chemical equations for all the chemical reactions involved.
Ans. An organic compound ethanol on heating with conc. H₂SO₄ forms a compound ethene which on addition of one molecule of hydrogen in the presence of nickel forms a compound ethane .One molecule of ethane on combustion form two molecules of CO₂ and three molecules of H₂O. 
X is ethanol, Y is ethene and Z is ethane.
 C₂H₅OH -( H₂SO₄) →C₂H₄  + H₂ →C₂H₆ + O₂→ CO₂ +  H₂O.

78. Define structural isomers.Write the structural formula of all the isomers of hexane.Explain why propane cannot exhibit this property. 
Ans .Compounds with identical molecular formula but different structures are called structural isomers. 
Structure of hexane.
                             H   H   H   H   H   H                     H    H      H     H     H
Straight chain-        l     l    l     l    l    l                       l     l       l       l      l
                       H - C - C - C - C - C - C- H         H -   C -   C -   C -   C -   C - H 
                             l    l     l    l     l    l                       l      l       l      l      l    
                            H   H    H  H    H   H                     H    H  H- C- H H    H

                                                                                                 l

                                      H                                                    H
                                       l 

                                      C

                                   //    ∖                                       Branched chain
                           H ― C       C ―H
                                  l          ll
                           H ― C       C ―H
                                   \\   ／ 
                                      C
                                       l   Cyclic chain
                                      H
79. List any four differences between soap and detergent.
Ans. (i) Soaps are produced by the specification method.
Detergent are made from synthetic source.
(ii) Soaps are alkaline in nature .
Detergents are carbonic compounds which are not alkaline.

(iii) Soaps are biodegradable .

Detergents are non biodegradable.

(iv) Soaps don't produce lather with hard water and are not able to clean the cloth. Detergents clean the cloth even in hard water. (v) Lot of water is needed to remove soap from the cloth. Detergents are removed very easily so less quantity of water is needed.

80. Match the reactions given in Column I with the names given in column II. 

1. Column I

    (a) CH₃OH +CH₃COOH-> CH₃COOH + H₂O

·   (b) CH₂=CH₂ + H₂ ->CH₃ – CH₃ (Ni)

·   (c) CH₅ + Cl₂ -> CH₃Cl + HCl

·  (d) CH₃COOH + NaOH-----> CH₃COONa +H₂O

     Column II

·   (i) Addition reaction

·   (ii) Substitution reaction

·   (iii) Neutralization reaction

·   (iv) Esterification
Ans. (a) CH₃OH +CH₃COOH-> CH₃COOCH₃ + H₂O  -- (iv) Esterification.
(b) CH₂=CH₂ + H₂ ->CH₃ – CH₃ (Ni) ---- (i) Addition reaction.
(c) CH₅ + Cl₂ -> CH₃Cl + HCl ---(ii) Substitution reaction.
(d) CH₃COOH + NaOH-----> CH₃COONa +H₂O ----(iii) Neutralization reaction.

                                **************
     Do your self 👇

1. Give at least one example in each case to show structure of simmers of :
   (a) Single bond compound
   (b) Double bond compound
   (c) Triple bond compound.
2. Name a compound of each type and draw the figure. 
   (a) Cyclic compound with single bond
   (b) Cyclic compound with double bond.
   (c) Cyclic compound with triple bond .
3. What would be observed when adding a 5% alkaline potassium permanganate drop by drop to some worm ethanol taken in a test tube . Write the name of the compound formed during the chemical reaction. 
4. Draw the structure of possible isomers of butane C₄H₁₀.
5. Draw the structure of CH₃COOH molecule.
6. A compound C reacts with any metal to form a compound and evolves a gas which burns with a Pop sound. Compound C on treatment with an alcohol A in the presence of an acid forms a sweet smelling compound S. On addition of NaOH to C, it also gives R and water. S on treatment with any NaOH Solutions give back R and A. Identify C, R, A, S and write down the reactions involved.
7. Name the functional group present in.
   (i) CH₃COCH₃ and state the name of this compound.
   ii) CH₃CHO         
   (iii) C₂H₅Cl
   (iv) C₂H₅OH
   (v) C₂H₅COOH.
   (vi) HCOOH
8. Draw the electron-dot structure structural formula of
   (i) Ethane (ii) Ethene (iii) Acetic Acid (iv) Butanon.
9. Complete the following:
   (i) CH₃CH₂OH.(conc.H2SO4)→ ?
   (ii) CH₃COOH + KHCO₃ (sunlight) →?
   (iii) CH₃COOC₂H₅⇾ (NaOH) ---------?
   (iv) CH₃COOH + NaHCO₃➝------?
   (v) CH₄ + Cl₂.(sunlight) ➝------?
10. Write the name of the following:
    (a) CH₃CH₂Br,   (b) CH₃CH₂CH₂CHCHCH₃
11. Complete the following reaction:
    (a) CH₃CH₂OH (alkaline KMNO4) → ?    
    (b) 2Na + 2CH₃CH₂OH→ ? + ?
    (c) CH₃COH + CH₃CH₂OH (acid)→ ?
12.  Complete the following equations
    (i) nCH₂ =  CH₂→---------?
    (ii) CH₃COOH + NaHCO₃→ ---?---- +---?---+ --?-----.
13. (a) Write the name of the following:
    CH₃CH₂COOH, CH₃CH₂CH₂Br
    (b) Draw the electron dot structure of an organic compound.
14. How are following products obtained from ethanol?
15. (i)  Ethyl ethanoate.(ii) Sodium ethoxide.
16. (i) Name and draw the chain structure and dot Structure of first two alkanes.
    (ii) Write the name of the following:
    (a) CH₃CH₂CCH (b) CH₃CH₂OH  (c) CH₃CO CH₃ .
17. With the help of a diagram explain cleansing action of soap.
    (i) Identify from the following the hydrocarbons that can undergo addition reaction. C₃H₄,  C₂H₆,  CH₄, C₂H₄. Justify your answers.
    (ii) Write the name of the homologous series to which they belong to.
18. An organic compound A of molecular formula C₂H₄ on reduction gives another compound B of molecular formula C₂H₆. B on reaction with chlorine in the presence of sunlight gives C of molecular formula C₂H₅Cl.
19. (i) Name the compound A,B, and C.
    (ii) Write the chemical equations for the conversion of A to B and name the type of reaction..
20. Make the structure of methane by showing sharing of electrons between carbon and hydrogen atoms. How could you convert methane into chloroform by substitution reaction? Explain with the help of chemical reactions.
21. Draw the possible isomers of the compound with molecular formula C₃H₆O and also give their electron dot structures.