Ans: (c)

Ans: (a) (i) When ethanol is heated with cone. H₂SO₄ at 443 K, ethene is obtained due to dehydration of ethanol.
(a) (ii) When 5 % alkaline KMnO₄ solution is added drop by drop to warm ethanol then it gets oxidized to ethanoic acid.

(b) Addition reactions : Those reactions in which atoms or group of atoms are simply added to a double or triple bond without the elimination of any atom or molecule, are known as addition reactions.

Substitution reactions: The reactions which involve the displacement or substitution of an atom or a group of atoms in an organic compound by another atom or group of atoms, are known as substitution reactions.

Saturated hydrocarbons are fairly unreactive and inert in the presence of most of the reagents. However, in presence of sunlight, hydrocarbons undergo rapid substitution reactions, e.g.,

Ans: (a) A homologous series is the family of organic compounds having the same functional group, similar chemical properties but the successive (adjacent) members of the series differ by a -CH2 unit or 14 mass units.
For example, alkane series has general formula CnH2n + 2.
First member of homologous series of alkane is .methane, i.e., CH4.
Second member of homologous series of alkane is ethane, i.e., C2H6.
Third member of homologous series of alkane is propane i.e., C3H8.  
(b) (i) Carboxylic acids react with alcohols in the presence of a little concentrated sulphuric acid to form pleasant smelling esters. This reaction is called esterification reaction.

(ii) Addition reactions : Those reactions in which atoms or group of atoms are simply added to a double or triple bond without the elimination of any atom or molecule, are known as addition reactions.

Ans: (a)
Pure ethanoic acid or acetic acid freezes below room temperature into white crystals that resemble glaciers. 

Ans: (b)
When an ester reacts with the base saponification reaction occurs.  

Ans: (i) 5% solution of KMnO₄ is prepared by adding 5 g of KMnO₄ in 95 g of water.
(ii) Here alkaline KMnO₄ acts as an oxidising agent. It oxidises ethanol to ethanoic acid by donating nascent oxygen. If excess of KMnO₄ is added the purple colour will persist indicating no more alcohol is left and there is no reaction.

Ans: Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called catenation. Carbon shows catenation due to its small size and Stronger carbon-carbon bond strength. As we move down the group, the element-element bond energies decrease rapidly. For this reason other elements of this group show little or no catenation property.

Ans: (a)
The given compounds are members of homologous series of alcohol.

Ans: Benzene is a cyclic unsaturated carbon compound.

Ans: Covalent compounds have low melting and boiling points because the forces of attraction between molecules of covalent compounds are very weak. On applying a small amount of heat these molecular forces break.  

Ans: (a) Isomers are those molecules which have the same molecular formula but different structural formula i.e., show different properties.

(b) 

(c)  (i) When ethanol is heated with conc. H₂SO₄ at 443 K, ethene is obtained due to dehydration of ethanol.

(c) (ii) Propanol to propanoic acid

Ans: 
Ethanol having chemical formula C₂H₅OH is the active ingredient of all alcoholic drinks.
Uses of ethanol:
1. Ethanol is widely used in industry as a solvent.
2. Ethanol is used as an antiseptic for wounds in the form of rectified spirit.
Chemical equations: 

(i) 2C₂H₅OH + 2Na → 2C₂H₅O^–Na⁺ + H₂ ↑ 

(ii)

Ans: 
(a)  Ionic compounds are formed either by gaining or losing electrons from the outermost shells, but carbon which has four electrons in its outermost shell cannot form ionic bonds because
1. If carbon forms ionic bonds by gaining four electrons to attain a noble gas configuration then it would be difficult for six protons in the nucleus to hold ten electrons.
2. If carbon forms ionic bonds by loss of four electrons then it would require a lot of energy to remove these electrons from outermost shell.
Due to these reasons carbon forms covalent bonds by sharing the valence electrons.
Type of bonds formed in ionic compounds are called electrovalent bonds and the type of bonds formed in carbon compounds are called covalent bonds. 

(i) Covalent bonds are those bonds which are formed by sharing of the valence electrons between two atoms. 

 Electron dot structure of Methane

Covalent compounds are generally poor conductors of electricity because they do not have tree electrons or ions. 

(ii) Covalent compounds have low melting and boiling points because the forces of attraction between molecules of covalent compounds are very weak. On applying a small amount of heat these molecular forces break.

(b) Structural formula of Benzene, C₆H₆ is shown below

Ans: 
(i) Methane is the first member of alkane series having formula CH₄.
Covalent bonds are those bonds which are formed by sharing of the valence electrons between two atoms. Electron dot structure of methane is shown in the figure. 

 Electron dot structure of Methane

Covalent compounds are generally poor conductors of electricity because they do not have tree electrons or ions.
(ii)  When methane is burnt in presence of oxygen then carbon dioxide will be produced.
CH₄ + O₂ → CO₂ + H₂O + heat + light 
Covalent compounds have low melting and boiling points because the forces of attraction between molecules of covalent compounds are very weak. On applying a small amount of heat these molecular forces break.

Ans: (i) Methane is the simplest hydrocarbon which is produced when carbon atom shares its 4 valence electrons with 4 hydrogen atoms.
(ii) Methane achieves noble gas electronic configuration by sharing its four electrons with other elements, i.e. it forms covalent compounds.

Ans: Covalent compounds can be formed by carbon.

Ans:

• Vegetable oil undergoes hydrogenation to form saturated product known as vegetable ghee or vanaspati ghee. This reaction is known as hydrogenation of oils.
• Vegetable oil is liquid at room temperature whereas vegetable ghee is solid at room temperature.
• Nickel acts as catalyst and forms saturated hydrocarbons.

Ans: 
(a) Carbon compounds are covalent in nature and they do not dissociate to form ions because of which they are poor conductors of electricity.
(b) Cyclohexane is the saturated compound in which the carbon atoms are arranged in a ring.

Cyclohexane

It has 18 single bonds.

Ans: The compounds A, B, C and D are given as under:
A = CH₃COOH
B = CH₃COONa
C = C₂H₅OH
D = CH₃COOC₂H₅
The reactions are explained as under:

Ans:  ‘X’ (C₄H₈) will show addition reaction because it is unsaturated, i.e. it has a double bond e.g.

 When a molecule or a compound is added to unsaturated compound to form a saturated compound is called addition reaction.

Ans: (i) CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH
(ii) CH₃COOH + NaOH → CH₃COONa + H₂O
(iii) C₂H₅OH + CH₃COOH → CH₃COOC₂H₅ + H₂O

Ans: CH₃—CH₂OH is structural formula of ethanol
Physical properties:
(i) It is liquid and has sweet smell.
(ii) It is soluble in water in all proportions.
When ethanol is heated with cone. H₂SO₄ at 443 K, ethene is formed.

Conc. H₂SO₄ acts as dehydrating agent.

Ans:
(i) The compound formed is ‘Esters’ It has a pleasant fruity smell.

(ii) 
Conc. H₂SO₄ acts as dehydrating agent.
(iii) It is used as a solvent in glass, nail polish removers and decaffeinating tea and coffee. It is used is solvent in printing to modify its drying rate.
Uses of esters:

• Esters are used as flavouring agents in ice creams, cold drinks etc.
• They are used in perfumes.

Ans:

Uses:
(i) Esters are used in cold drinks, ice creams, perfumes and as artificial flavouring agents.
(ii) Saponification process is used in manufacture of soaps.

Ans: Alkaline KMnO₄/NaOH (Potassium permanganate) and Acidified K₂Cr₂O₇ / H₂SO₄ (Potassium dichromate).

Ans: A series of compounds whose two successive members differ by - CH₂ in the molecule formula and which show similar chemical properties are called homologous series.

Characteristics:
1. Melting and boiling points increase regularly with increase in molecular mass.
2. Solubility in a particular solvent shows a regular gradation.
3. Chemical properties remain the same in the homologous series.
Next higher homologue of HCOOH is CH₃COOH. Its name is ethanoic acid or acetic acid.

Ans:

(i) Fruity smelling compounds belong to the class of esters.

(ii) Conc. H₂SO₄ acts as a dehydrating agent and removes the water formed in the reaction.

Ans: Soaps are sodium or potassium salts of fatty acids having —COONa group. Detergents are sodium or potassium salts of sulphonic acids having — SO₃Na and —SO₄Na group.
Cleansing Action of Soap. Soaps consist of a large hydrocarbon tail which is hydrophobic (water-hating or water repelling) with a negatively charged head which is hydrophilic (water-loving) as shown in figure.

When a soap is dissolved in water, the molecules associate together as clusters called micelles in which, water molecules being polar in nature, surround the ions and the hydrocarbon part of the molecule attracts grease, oil and dirt.Hard water has Ca²⁺ and Mg²⁺ ions when they react with soap to form insoluble compound and soap goes waste.
Disadvantages of Detergents
(i) Detergents are expensive.
(ii) Many detergents are branched chain hydrocarbon which are not biodegradable and create water pollution.

Ans:

Covalent compounds are the compounds that contain covalent bonds in the molecule. A covalent bond is formed by sharing of electrons between the atoms.
While a covalent compound contains covalent bonds, the ionic compound is made up of ionic bond which is formed by transference of electrons from one atom to the other.
Characteristics of covalent compounds:
(i) These compounds show low melting points and boiling points because the intermolecular forces are weak.
(ii) Such compounds are poor conductors of electricity.
(iii) Generally insoluble or less soluble in water but soluble in organic solvents.

Ans:

Ans: The structures of the aldehyde and ketone with the molecular formula C₃H₆O are

Both these compounds are isomers (because they have the same molecular formula but different structural formula).

Ans:
(i) Ethanol reacts with sodium metal whereas methyl ethanoate does not. They differ in functional group, and in chemical properties.
(ii) It is because it has pleasant fruity smell.
(iii) 

Ethanol gets dehydrated with conc. H₂SO₄ to form ethene and H₂O.

Ans:

(a) It is an atom or group of atoms or reactive part of compound which largely determine the chemical properties of compound (i) Methanol (ii) Ethanoic acid.

(b) 

Alkaline KMnO₄ acts as an oxidizing agent.

Ans:
‘X’ is C₂H₅OH

2C₂H₅OH + 2Na → C₂H₅Na + H₂
‘Y’ is H₂(g) which burns with ‘pop’ sound.

Ethene is the product.

Ans: 

‘P ’ is C₂H₅OH, Ethanol

Q is Acetic Acid.
2CH₃COOH + 2Na → 2CH₃COONa + H₂
‘R’ is hydrogen gas which burns with ‘pop’ sound.

Ans:

(a) Add sodium hydrogen carbonate. Ethanol will not react. Ethanoic acid will give brisk effervescence due to carbon dioxide.
(b) Pure ethanoic acid exists as solid like glaciers at 291 K, therefore, called glacial acetic acid.

Ans:

(a) 2CH₃COOH + 2Na → 2CH₃COONa + H₂
Sodium ethoxide is the main product formed.
(b) CH₃COOH + NaOH→ CH₃COONa + H₂O
Sodium ethoxide is the main product formed.

(c)

Ethyl ethanoate (ester) is the main product formed.

Ans: When complete oxidation of fuel takes place with the release of high amount of heat and light, it is called combustion reaction. It is highly exothermic and generally accompanied by evolution of heat and light.
Examples - Burning of coal
C + O₂ → CO₂ + heat + light
Burning of the rocket fuel (liquid H₂)
2H₂O + O₂ → 2H₂O + heat + light
Burning of acetylene used in welding torches.
2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O + heat + light

Ans:  (i) The series of organic compounds which have similar chemical properties, same functional group and same general formula is called homologous series.
(ii) It is because C₅H₁₀ has higher molecular weight, more Vander Wall’s force of attraction and higher boiling points and melting points.
(iii) C₃H₆ < C₄H₈ < C₅H₁₀ is increasing order of boiling point.

Ans:

They are functional isomers.

Ans:
Ethanol, C₂H₅OH

Conc. H₂SO₄ acts as dehydrating agent.

Ans:
Those substances which add oxygen are called oxidising agent and propanoic acid is formed.

Reaction of Propanol with Oxidizing Agent
Propanol will get oxidised to propanoic acid by acidified KMnO₄.

Ans:
(a) Add bromine water. Unsaturated hydrocarbon will decolourise bromine water whereas saturated hydrocarbon will not.
(b) Carbon dioxide and Water are formed.

2C₂H₆ (g) + 7O₂ (g) → 4CO₂ (g) + 6H₂O +Heat + Light
(c) It is because hydrogen atom of methane gets substituted by chlorine atom to form chloromethane, therefore, it is called a substitution reaction.

Ans:  Micelles: When molecular ions in soaps and detergents aggregate, they form micelles.
It is because a large number of molecular ions of soaps get aggregated and form colloidal solution. Soap has hydrophobic tail (hydrocarbon) which dissolves in hydrocarbon part and hydrophilic part dissolves in water. Ethanol is non-polar solvent therefore micelles are not formed because hydrocarbon part gets attracted towards ethanol and the ionic end will not dissolve in alcohol.

Ans: The compounds are identified as under:
P = Ethanol (CH₃CH₂OH)
Q = Ethene (CH₂ = CH₂)
R = Ethane (CH₃ – CH₃)
Reactions are given as under:

Ans:

Electron-dot structure of Ethyne

Ethyne and air will not produce enough heat due to incomplete combustion needed for welding purpose. Ethyne and oxygen will produce a lot of heat due to complete combustion which can be used for welding purposes.

Ans: Isomers are those compounds which have the same molecular formula but different structural formula.

Butane & Iso-Butane are two isomers of C₄H₁₀. Isomers are not possible for the first three members because branching is not possible.

Ans:  C_nH_2n and C_nH_2n- 2 are the general formula of alkene and alkynes in which addition reaction with hydrogen is possible. Hydrogen is added to unsaturated hydrocarbon (having double or triple bond) in presence of heated nickel as catalyst.

Ans:
(i) Ethane (C₂H₆)

(ii) Ethene (C₂H₄)

(iii) Ethyne (C₂H₂)

Ans:
(i) CH₄ + 2O₂ → 2H₂O + CO₂
Water and carbon dioxide formed.

(ii)

The concentrated sulphuric acid can be regarded as a dehydrating agent which removes water from ethanol.

(iii) 

 Esters are sweet smelling substances.

Ans:
Alkaline KMnO₄ is dark pink in colour. So when it is added to ethanol and heated, the pink colour of the solution disappears. When excess of KMnO₄ is added, the pink colour does not disappear, indicating that all the ethanol has been converted to ethanoic acid.
• Physical properties of ethanol:
(a) It is a colourless liquid with pleasant smell and burning taste.
(b) It is a volatile liquid with low boiling point.
• Uses of ethanol:
(a) It is used in the manufacture of medicines, varnished, paints, dyes, soap, etc.
(b) It is a good solvent. Many organic compounds which are insoluble in water are soluble in ethanol.

Ans:
Soaps are sodium or potassium salts of long chain carboxylic acids.
Detergents are ammonium or sulphonate salts of long chain carboxylic acids.

Cleansing action of soap: The ionic end of soap dissolves in water while the carbon chain dissolves in oil. Soap molecules form micelles where one end of the soap molecule is linked to oil droplet while the ionic part faces water. This forms an emulsion in water. On adding water, these micelles containing dirt are washed away and our clothes are washed clean. This is represented in the figure.

Ans: Conversion of oil into fat by passing hydrogen gas in the presence of nickel as catalyst is called hydrogenation. This is how hydrogenation is carried out.
Conditions: The presence of a catalyst like nickel is essential.
Change in physical property: Oils are liquids while the fats obtained on hydrogenation are solids i.e., a change in the physical state takes place on hydrogenation.

Ans: Carbon has no tendency to lose electrons easily. Similarly it has no tendency to gain electrons. It completes its octet by sharing the electrons with other atoms. Therefore, carbon forms compounds mainly by covalent bond.
Two main reasons for carbon forming a large number of compounds are given below:
Catenation: It is the property of carbon to link with other carbon atoms to form straight chain, branched chain or cyclic compounds. Thus, carbon forms a large number of compounds containing 2, 3, 4, 5,....etc., carbon atoms.
Tetravalency: Carbon has four electrons in the outermost shell. It shares these four electrons with four electrons from four other monovalent atoms. Carbon has the tendency to form bonds with hydrogen, oxygen, nitrogen and halogens. This increases the number of compounds of carbon.
Carbon forms strong bonds with most other elements: This is because carbon has a small atomic size. It can hold strongly the four pairs of electrons that it shares with other atoms. Therefore, it forms strong bonds with other elements.