04.Carbon and its Compounds

Carbon is found in earth crust 0.02 % in the form of minerals and found in atmosphere 0.03 % in the form of CO₂
Bonding in Carbon – The Covalent Bonding
The atomic number of carbon is 6. Carbon has four electrons in its outermost shell and carbon needs to gain or lose four electrons to attain noble gas configuration.
▶If the carbon atom gains four electrons to form anion then, it is difficult for a nucleus with six protons to hold on to ten electrons.
▶If the carbon atom loses four electrons to form cation then, it requires a large amount of energy to remove four electrons.
Thus, carbon overcomes this problem by sharing of its valence electrons with other atoms. The shared electrons ‘belong’ to the outermost shells of both the atoms and lead to both atoms attaining the noble gas configuration.

Electron Dot Structure of Hydrogen

H-H
Electron Dot Structure of Oxygen

Electron Dot Structure of Nitrogen

N ≡ N
Electron Dot Structure of Chlorine

Cl - Cl
Electron Dot Structure of Sulphur

Allotropy

Different forms of an element which have different physical properties but their chemical properties are same are called allotropes and this property is called Allotropy

.Allotropes of Carbon:

1. Crystalline allotropes - Diamond, Graphite, Fullerene

2. Amorphous forms – coal, coke, wood charcoal, animal charcoal, soot, gas carbon

Both diamond and graphite are made of carbon atoms but there is a difference between diamond and graphite.

1. Diamond is the hardest substance known while graphite is smooth and slippery.

2. In diamond each carbon atom is bonded to four other carbon atoms whereas in graphite each carbon atom is bonded to three other carbon atoms

3. The structure of diamond is tetrahedral while the structure of graphite is formed by the hexagonal layers

4. In diamond, all four valences of carbon are attached to four other carbon atoms, so due to the absence of free electrons, diamond is a bad conductor of electricity, while in graphite, three valences of carbon are attached to three other carbon atoms, so due to the presence of free electrons, graphite is a good conductor of electricity

Fullerenes: Fullerenes are allotropes of carbon. The first to be identified was fullerene C-60, which has carbon atoms arranged in the shape of a football. Fullerene was named by famous architect Buckminster Fuller.

Versatile Nature of Carbon:

The two properties of carbon, that are tetravalency and catenation, enables carbon to form a large number of compounds.

1. Catenation : Carbon has the unique ability to form chain by forming covalent bonds with other atoms of carbon. This property is called catenation.

Due to this property, carbon forms bonds with other carbon atoms to form straight chains, branched chains and ring type chain.

In addition, carbon atoms may be linked by single, double or triple bonds.

2. Tetravalency: Carbon has four electrons in its outermost shell i.e. the valency of carbon is four. so it is capable of bonding with four other atoms of carbon or atoms of any other mono-valent element.

Hydrocarbons : The chemical compounds which are made up of only carbon and hydrogen are called hydrocarbons. There are two types of hydrocarbon:

Saturated Hydrocarbons :- Hydrocarbons, in which the carbon atoms are connected by only single bonds are called saturated hydrocarbons. such as alkanes.

Unsaturated hydrocarbons : - Hydrocarbons, in which two carbon atoms are connected by double or triple bonds are called unsaturated hydrocarbons, such as alkene and alkyne.

Alkane: Alkanes are saturated hydrocarbons.
General Formula : CₙH₂n₊₂
Ex. Methane :
Methane is the simplest compound of carbon. Methane is the most commonly used fuel and is a major component of biogas and compressed natural gas (CNG).
Molecular Formula : CH₄
Structural Formula

Electron Dot Structure of Methane

Ex. Ethane :
Moleular Formula C₂H₆
Structural Formula

Electron Dot Structure

Ex. propane
Molecular Formula C₃H₈
Structural Formula

Ex. Butane
Molecular Formula C₄H₁₀
Structural Formula

Ex. Pentane
Molecular Formula C₅H₁₂
Structural formula

Ex. Hexane
Molecular Formula C₆H₁₄
Structural Formula

Structural isomers: Compounds that have the same molecular formula but different structural formulas are called structural isomers. like n-butane and iso-butane (both C₄H₁₀)

n-butane iso-butane
Alkene or olefin –Alkenes: ㅡC＝Cㅡ
These are unsaturated hydrocarbons, in which two carbon atoms are connected by double bond.
General formula: C_nH_2n
Ex. Ethene
Molecular Formula C₂H₄
Structural formula

Electron Dot Structure

Alkyne or Acetylene – Alkynes: ㅡC≡Cㅡ
These are unsaturated hydrocarbons, in which two carbon atoms are connected by triple bond.
General Formula: C_nH_2n-2
Ex. Ethyne
H-C ≡ C-H
Cyclic hydrocarbon. :The hydrocarbon , in which the carbon atoms are arranged in the form of ring are called cyclic hydrocarbon. eg, cyclohexane, benzene

Cyclohexane Benzene

Homologous Series:

Any two member of the homologous series differ by – CH₂ group and difference in molecular mass is 14µ.
Homologous Series: A series of compounds in which hydrogen in a carbon chain is replaced by the same functional groups is called Homologous Series.
Hetero atoms : An element or group of elements that replace one or more hydrogen (H) atoms from hydrocarbon are called hetero atoms.
Functional Group: An atom or group of atoms present in a molecule which determines its chemical properties are called Functional Group.
Name of functional group -
Heteroatom      Fanctional group Formula
Cl/Br halo -alkane —Cl, —Br
(Chloro / Bromo)
Oxygen (i) Alcohol              —OH
(ii) Aldehyde

(iii) ketone

(iv) Carboxylic acid

Nomenclature of Carbon Compounds
The name of an organic compound can be divided into three major parts, namely:
1. Root word 2.Primary suffix 3.Secondary suffix
Root word : The Word root indicates the total number of carbon atoms present in the longest carbon chain
No. of carbon atoms Rootword
         1                Meth
         2        Eth
         3                 Prop
         4          But
         5        Pent
         6        Hex
         7        Hept
         8        Oct
         9        Non
         10 Dec
Primary suffix
Primary suffix indicates saturation or unsaturation of a hydrocarbon. This is attached to the root word.
Saturated hydrocarbon          → ane
Double bonded unsaturated hydrocarbon → ene
Triple bonded unsaturated hydrocarbon    → yne
Secondary suffix : Secondary Suffix is generally written after the primary suffix is written .It represents the functional group attached to the carbon chain.

CHEMICAL PROPERTIES OF CARBON COMPOUNDS
1. Combustion : All the compounds of carbon burn in oxygen (air) and give
C + O₂ → CO₂ + heat and light
CH₄ + O₂ → CO₂ + H₂O + heat and light
CH₃–CH₂OH + O₂ → CO₂ + H₂O + heat and light
Saturated hydrocarbon generally burn in air with clean blue flame. But, in limited supply of air saturated hydrocarbon burn with sooty flame due to incomplete combustion. Unsaturated hydrocarbons burn in air with yellow flame with black smoke. The gas/kerosene stove used at home has inlets for air so that sufficient oxygen is available for the complete burning of the fuel to produce a smokeless blue flame. If the bottoms of cooking vessels getting blackened, it means that the air holes of stove are blocked and fuel is getting wasted. Due to presence of small amount of nitrogen and sulphur, coal and petroleum produces oxides of nitrogen and sulphur which are major pollutant in the environment

Oxidation
Carbon compounds are easily oxidised in the presence of oxidizing agents. When ethanol is heated with alkaline potassium permanganate or acidic potassium dichromate it oxidises in acetic acid [ethanoic acid].

Oxidising agent
Substance which oxidizes other substances by giving them oxygen are called oxidising agent
Addition Reaction
Unsaturated hydrocarbons react with hydrogen in the presence of catalysts such as palladium or nickel to form saturated hydrocarbons. This reaction is commonly used in the hydrogenation of vegetable oils. Vegetable oils generally have long unsaturated carbon chains while animal fats have saturated carbon chains. Animal fats generally contain saturated fatty acids which are harmful for health. Oils containing unsaturated fatty acids which are good for health. For this reason it is better to use vegetable oil for cooking.

Substitution Reaction
Saturated hydrocarbons react with chlorine in the presence of sunlight, chlorine is added to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen atoms one by one. When methane reacts with chlorine in sunlight, it forms methyl chloride (chloromethane) and hydrochloric acid.
CH₄ + Cl₂ → CH₃Cl + HCl (in the presence of sunlight)

Ethanol
Ethanol is a liquid at room temperature Ethanol is commonly called alcohol. Ethanol is an important component of all alcoholic drinks .Alcohol is a good solvent, so it is used in medicines like tincture iodine, cough syrup
1. Reaction of ethanol with sodium :
Ethanol reacts with sodium to form sodium ethoxide and hydrogen gas.
2Na + 2CH₃CH₂OH → 2CH₃CH₂O–Na⁺ + H₂
2. Formation of unsaturated hydrocarbons :
When Ethanol is heated with excess H₂SO₄ at 443K, dehydration reaction occurs and ethene and water are formed as by product. In this reaction, sulfuric acid acts as a dehydrating agent which removes water from ethanol.

Effect of alcohol on living beings :
When large quantities of ethanol are consumed, it slow down 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 commercial alcohol is made unfit for drinking by mixing in it some poisonous substances like methanol. and some dyes are added for identification This is called denatured alcohol.

Ethanoic acid :
Ethanoic acid is commonly called acetic acid. 5-8% solution of acetic acid in water is called vinegar and is used as a preservative in pickles. The melting point of pure ethanoic acid is 290 K and hence it often freezes during winter in cold climates. This gave rise to its name glacial acetic acid.
Reactions of ethanoic acid:
(i) Esterification reaction: Esters are most commonly formed by reaction of an acid and an alcohol. When ethanoic acid reacts with ethyl alcohol in the presence of an acid catalyst, ethyl acetate (ester) is formed. This reaction is called esterification.

Generally, esters are sweet-smelling substances. These are used in making perfumes and as flavouring agents.
The ester reacts with sodium hydroxide to form an alcohol and a sodium salt (sodium ethanoate or sodium acetate) and water. This reaction is called saponification because it is used to make soap. Soaps are sodium or potassium salts of long chain carboxylic acids.

Reaction with base: Ethanoic acid reacts with sodium hydroxide to form sodium acetate (acetate (salt)) and water.
NaOH + CH₃COOH → CH₃COONa + H₂O

Reaction of ethanoic acid with carbonate and hydrogen carbonate : Ethanoic acid reacts with carbonate and hydrogen carbonate to form salt, carbon dioxide and water.
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

SOAPS AND DETERGENTS
The soaps are sodium or potassium salts of long-chain carboxylic acids. Soap is cannot be used in hard water, because hard water contains calcium and magnesium ions. Soaps form insoluble precipitates with these ions in hard water.

Detergents are generally sodium salts of sulphonic acids or ammonium salts of amines with chlorides or bromides ions. Detergents do not form insoluble recipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hard water.

Cleaning Process of Soap and Micelle
Soap molecule has two dissimilar ends. At one end is the hydrocarbon chain which is non-polar and oil-soluble (hydrophobic) whereas at the other end is the carboxylate ion which is polar and water soluble (hydrophilic). Thus, a non-potartait is soluble in oil/grease. whereas a polar head is water- soluble. When soap is at the surface of water, its molecules arrange themselves in such a way that its ionic end is inside the water and the hydrocarbon tail is outside the water. When a cloth with dirty spots is soaked with soap solution, the dirt dissolves in the hydrophobic end of the soap and culster of molecules are formed 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. Soap in the form of a micelle is able to clean. because the oily dirt collected in the centre of the micelle. These micelles remain as colloidal solutions. Therefore, the dirt from the cloth is easily washed away

Select the saturated hydrocarbons from the following:
C₃H₆ , C₅H₁₀ , C₄H₁₀ , C₆H₁₄ , C₂H₄
C₄H₁₀ , C₆H₁₄ are saturated hydrocarbons.
State the valency of each carbon atom in (i) an alkane and (ii) an alkyne.
The valency of ‘C’ in alkane is 4. ii. The valency of ‘C’ in alkyne is also 4.
Carbon has four electrons in its valence shell. How does carbon attain stable electronic configuration?
Carbon shares four electrons to attain stable electronic configuration.
List two characteristic features of carbon which when put together given rise to a number of carbon compounds.
(a) Tetravalency (b) Catenation
Select alkenes and alkynes from the following: C₂H₄ , C₃H₄ , C₂H₂ , C₄H₈
Alkenes C₂H₄ , C₄H₃ Alkynes C₃H₄ , C₂H₂
Write the name and formula of fourth member of alkane series
CH₃ —CH₂ —CH₂ —CH₃ , Butane
A colourless gas X has a formula C₃H₆ . It decolourises bromine water. Write the chemical formula of ‘X’.
CH₂ =CH—CH₃ , Propene
Write the name and formula of 2nd member of homologous series having general formula CnH₂n .
CH₂ =CH—CH₃ is second member of alkene.
Write the name and formula of 2nd member of homologous series having general formula CnH₂n-₂.
HC ≡ C—CH₃ , Propyne
Write the name and molecular formula of the first member of homologous series of alkynes.
HC≡CH, Ethyne
The molecular formula of A is C₁₀H₁₈ and B is C₁₈H₃₆ . Name the homologous series to which they belong.
C₁₀H₁₈ belongs to alkyne, C₁₈H₃₆ belongs to alkene.
Write the name and formula of 2nd member of the series of carbon compounds whose general formula is CnH₂n.
CH₂ =CH—CH₃ , Propene
Write the name and formula of 2nd member of homologous series having general formula CnH₂n+₂.
CH₃ —CH₃ , Ethan
Butanone has four carbon per molecule of a compound. Name the functional group present in it.
Ketone
Write the name and formula of the second member of carbon compounds having functional group —OH.
CH₃ CH₂ OH, Ethanol
Write the names of next homologue of CH₃ CH₂ OH and HCOOH.
(i) CH₃ CH₂ CH₂ OH, Propanol (ii) CH₃ COOH, Ethanoic acid
Mention the functional group which always occurs at the terminal position of a carbon chain of an organic compound.
a. Aldehyde b. Carboxylic acid
Name the functional group present in each of the following compounds:
a. CH₃COCH₃(Propanone) b. C₂ H₅COOH (Ethanoic Acid)
a. Ketone b. Carboxylic acid
Name the functional group present in each of the following organic compounds:
a. C₂ H₅ —Cl b. C₂H₅OH
a. Halogen b. Alcohol
Write the name and formula of the 2nd member of the series of carbon compounds whose general formula is CnH₂n+1 —OH.
C₂ H₅ OH, Ethanol
Which of the following organic compounds belong to the same homologous series? C₂H₆ , C₂H₆O, C₂H₆O₂, CH₄O
C₂H₆O(C₂H₅OH) and CH₄O(CH₃OH) belong to same homologous series.
Write the balance chemical reaction of combustion reaction
Or Write balanced equations for the burning of methane
(a) CH₄ + 2O₂ ➞ CO₂ + 2H₂O + heat and light
Name the process by which unsaturated fats are changed into saturated fats.
Hydrogenation
State the difference between oils and fats.
Oils are unsaturated whereas fats are saturated compounds.
Name two oxidising agents that are used to convert alcohols to acids.
(i) Alkaline KMnO₄ (ii) Acidified K₂Cr₂O₇
What is glacial acetic acid? What is its melting point?
Glacial acetic is pure (100%) acetic acid. Its melting point is 290 K
Why are carboxylic acids called weak acids?
They do not ionise completely in aqueous solution
Will micelle formation take place when soap is dissolved in organic solvent. ?
No, micelles will not be formed in organic solvent.
Classify the following carbon compounds into two homologous series and name them.
C₃ H₄ , C₃ H₆ , C₄ H₆ , C₄ H₈ , C₅ H₈ , C₅ H₁₀
Alkene: C₃ H₆ , C₄ H₈ , C₅ H₁₀
Alkyne: C₃ H₄ , C₄ H₆ , C₅ H₈
Define the term functional group.
An atom or group of atoms present in a molecule which determines its chemical properties are called Functional Group.
Name the functional group in the following compounds:
a. CH₃—CH₂—CH₂—COOH b. CH₃—CO—CH₂—CH₃
a. Carboxylic acid b. Ketone
What is the difference in the molecular formula of any two consecutive members of homologous series of organic compounds?
The difference between successive members of homologous series is of —CH₂ unit.
Name the functional group present in each of the following compounds:
a. HCOOH b. C₂H₅CHO
a. Carboxylic acid b. Aldehyde
Write the molecular formula of first two members of homologous series having functional group —Cl.
(1) CH₃ - Cl Chloromethane
(2) CH₃-CH₂ - Cl Chloroethane
Write the molecular formula of first two members of homologous series having functional group —Br.
(1) CH₃ -Br Bromomethane
(2) C₂H₅ -Br Bromoethane
Write the molecular formula of first two members of homologous series having functional group -OH.
(1) CH₃ - OH Methanol.
(2) C₂H₅ - OH Ethanol.
Write the molecular formula of the first two members of the homologous series having functional group — COOH.
(1) HCOOH Methanoic acid
(2) CH₃ - COOH Ethanoic acid
Write the next homologue of propanol CH₃ CH₂ CH₂ OH and butanal CH₃ CH₂ CH₂ CHO.
a. CH₃ CH₂ CH₂ CH₂ OH, Butanol
b. CH₃ CH₂ CH₂ CH₂ CHO, Pentanal
Write the name of each of the following functional groups:
a. —OH b. >C=O
a. Alcohol b. Ketone
List two characteristics of covalent compounds.
(i) Low melting and boiling points ·
(ii) Bad conductors of electricity
Define catenation.
Carbon has the unique ability to form chain by forming covalent bonds with other atoms of carbon. This property is called catenation.
Which element exhibits the property of catenation to maximum extent and why?
Carbon because it can form strong covalent bond with other carbon atoms due to smaller size.
Unsaturated hydrocarbon gives a yellow flame with lot of black smoke when burnt in oxygen. Give reason.
Unsaturated hydrocarbons have more amount of carbon, therefore burns with smoky flame due to incomplete combustion.
What is meant by saturated hydrocarbon?
Those hydrocarbons in which valency of carbon is satisfied by single bonds only are called saturated hydrocarbons.
Name an element, other than carbon, which exhibits property of catenation up to seven or eight atoms. Are these compounds stable?
Silicon and Sulphur
No, these compounds are not stable
Name the products formed when ethane burns in air. Write the balanced chemical equation for the reactions showing two types of energies liberated.
When ethane burns in air carbon dioxide and water formed.
2C₂H₆ + 7O₂ ➞ 4CO₂ + 6H₂O + heat and light
What would be the electron dot structure of carbon dioxide which has the formula CO₂?
Write the molecular formula of 2nd and the 3rd member of homologous series whose first member is methane.
(1) CH₃—CH₃ Ethane
(2) CH₃—CH₂—CH₃ Propane
Explain why cannot we have isomers of first three members of alkane family ?
In the first three-member of alkanes, branching is not possible.
Therefore, isomers are not possible for the first three members of alkanes
Why is reaction between methane and chlorine in presence of sunlight is considered a substitution reaction.
It is because hydrogen atom is substituted by halogen atom, that is why it is called substitution reaction.
Write the molecular formula of 2nd and 3rd member of the homologous series whose first member is ethyne.
(1) HC ≡ C —CH₃ Propyne
(2) HC ≡ C—CH₂—CH₃ 1-Butyne
Write the molecular formula of 2nd and 3rd member of the homologous series whose first member is ethene.
(1) CH₂ =CH—CH₃ Propene
(2) CH₂ =CH—CH₂—CH₃ 1-Butene
What happens when a small piece of sodium is dropped into ethanol. ?
Ethanol reacts with Na to liberate H₂ gas and formed sodium ethoxide
2C₂H₅OH + 2Na ➡ 2C₂H₅ONa + H₂
Write the next homologue of each of the following:
a. C₂H₄ C₃H₆, CH₂ =CH—CH₃
b. C₄H₆ C₅H₈, HC≡C—CH₂ —CH₂ —CH₃
How is vinegar made?
vinegar is 5-8% solution of acetic acid in water. It is made by fermentation of sugars and starch. Ethanol is the intermediate product
What are esters? List two uses of esters.
Generally, esters are sweet-smelling substances. Its formula is R—COOR’.
These are used in making perfumes and as flavouring agents.
Why ethanoic acid is called glacial acetic acid?
The melting point of pure ethanoic acid is 290 K and hence it often freezes during winter in cold climates. So ethanoic acid is called glacial acetic acid
Write the name and formula of compounds formed when the ester CH₃COOC₂H₅ undergoes saponification.
Or Write the chemical equations when an ester reacts with a base?
CH₃COOC₂H₅ + NaOH ➞ CH₃COONa + C₂H₅OH
Sodium ethanoate Ethanol
Write the chemical reaction to convert ethanol into ethanoic acid.
C₂H₅OH ➞ AlkKMnO₄ ➞ CH₃COOH + H₂O
(Ethanoic Acid)
Methyl ethanoate is used in making perfume. Justify.
Methyl ethanoate is an ester and esters are sweet smelling (fragrant ) substance. Therefore, they are used in making perfume.
Write chemical name and formula of vinegar?
Chemical name - Ethanoic acid
Formula - CH₃COOH
State the reason for the suitability of detergents for washing even in case of water having calcium and magnesium ions.
Or Why are detergents preferred over soaps for washing clothes in hard water? Explain.
Detergents do not form insoluble recipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hard water.
How is scum formed.?
Or
Explain why washing clothes with hard water is not effective.
Ca²⁺ and Mg²⁺ ions present in hard water react with soap to form precipitates which is insoluble in water and called scum.
Explain why washing clothes with hard water is not effective.
Ca²⁺ and Mg²⁺ ions present in hard water react with soap to form precipitates which is insoluble in water and called scum.
Draw electron dot structures of C₂ H₅ OH
Draw the structure of ethanoic acid molecule, CH₃ COOH.
Draw the structure of butanone molecule, CH₃COC₂H₅ .
Draw the structure of the hexanal molecule C₅HnCHO.
Write the formula and electron dot structure of ethyne molecule
formula - C₂H₂
Write the formula and electron dot structure of ethene molecule
formula -C₂H₄
Write the formula and electron dot structure of ethane molecule ethane
formula - C₂H₆ .
Write the name and draw the structure of the second member of alkene series
Propene
Write the number of covalent bonds in the molecule of ethane.

It has 7 covalent bonds
Write the number of covalent bonds in the molecule of propane, C₃H₆.

It has 10 covalent bonds
Write the number of covalent bonds in the molecular formula of butane, C₄ H₁₀

It has 13 covalent bonds
Write the molecular formula of benzene and state the number of double bonds in its structure.

Benzene. These are 3 double bonds.
A molecule of ammonia has the formula NH₃ . Predict the total number of bonds present around nitrogen atom.

It has three covalent bonds
Draw the structure of simplest ketone.
Write the structural formula of chloroethane.
Name the functional groups of the following compounds:
a. b. c. R—OH d. R—X
a. Carboxylic acid b. Ester c. Alcohol d. Halogen
Write the formula of first two members of homologous series whose functional group is —CHO.

Methanal       Ethanal
Draw the structural formula of methanoic acid.
Write the name and structure of an aldehyde with four carbon atoms in its molecule.

Butanal
Write the name and structure of an alcohol with three carbon atoms in its molecules.

CH₃CH₂CH₂OH, 1-Propanol
Name the following compounds:
(i) CH₃CH₂OH
Ethanol
(ii)
Ethanal
Write the name and structure of an alcohol with four carbon atoms in its molecule.

CH₃ CH₂ CH₂ CH₂ OH, 1-Butanol
Name the following compound:

1-Hexyne
Write the formula of first two members of
homologous series whose functional group is >C = O

2-Propanone

2-Butanone
The formula of citric acid is shown below: State the name of —COOH functional group in citric acid.

Carboxylic acid
Write the name and formula of the first member of series of carbon compound having functional group —CHO.
Methanal
Write the name and formula of the first member of carbon compounds having functional group —COOH.
Methanoic acid
The structural formula of an ester is

Write the structural formula of the corresponding alcohol and acid.

Ethanoic Acid Ethanol
What is a homologous series of carbon compounds?
Homologous series is series of organic compounds which have same functional group and similar chemical properties and each successive member has more — CH₂ unit than the previous one.
How do the melting and boiling points of the hydrocarbons change with increase in molecular mass?
Melting and boiling point of the hydrocarbons increase with increase in molecular mass because as the molecular mass of molecules increases, The intermolecular forces of attraction increase.
C₃H₆ , C₄H₈ and C₅H₁₀ belong to same homologous series.
(i) Why the melting and boiling point of C₅H₁₀ is higher than C₄H₈ ?
C₅H₁₀ has higher molecular mass and more force of attraction, hence higher boiling point than C₄H₈.
(ii) Arrange these hydrocarbons in order of increasing boiling points.
C₃H₆ < C₄H₈ < C₅H₁₀
Why do alkanes burn with blue flame ?
The saturated hydrocarbon (alkanes) generally burn in air with a blue flame because the percentage of carbon in the saturated hydrocarbon is comparatively low which gets oxidised completely by oxygen present in air.
What is a saponification reaction. Give one example
The ester reacts with sodium hydroxide to form an alcohol, a sodium salt and water. This reaction is called saponification because it is used to make soap.
CH₃COOCH₃ + NaOH ➞ CH₃COONa + CH₃OH
What are soaps ? Why do they form scum with hard water?
The soaps are sodium or potassium salts of long-chain carboxylic acids. Ca²⁺ and Mg²⁺ ions present in hard water react with soap to form precipitates which is insoluble in water and called scum.
Chemical properties of ethanol is different from methyl ethanoate. Justify the statement with proper reason.
Chemical properties of a compound depends on its functional group. Ethanol and methyl ethanoate have different functional group. Ethanol has —OH functional group.While ethanoate has >C =O functional group thus they behave differently.
Under which condition an oxidation reaction can be called as combustion reaction. Illustrate your answer with example.
When oxidation reaction produces heat as well as light it is called combustion reaction. CH₄ + 2O₂ ➞ CO₂ + 2H₂O + heat + light
It is oxidation as well as combustion reaction.
What are micelles?
Micelles are cluster of molecules of soap in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. The soap in the form of a micelle is able to clean.
Name the carbon compound which on heating with excess of cone. H₂SO₄ at 443 K gives ethene. Write the chemical equation of the reaction stating the role of conc H₂SO₄ in it
Or Ethanol is converted into ethene when excess of cone. H₂ SO₄ is added. Justify with the help of reaction.
Or Write the name and molecular formula of an organic compound having its name suffixed with ‘—ol’ and having two carbon atoms in the molecule. With the help of a balanced chemical equation indicate what happens when it is heated with excess of cone. H₂SO₄
Or Write a chemical reaction to show dehydration of ethanol.
CH₃CH₂OH . ➡443K ConcH₂SO₄ ➡ CH₂ =CH₂ + H₂O
Ethanol
Conc H₂SO₄ acts as dehydrating agent in this reaction
What happens when ethyl alcohol and acetic acid react with each other in presence of cone. H₂SO₄ ?
Or Name the compound formed when ethanol is warmed with ethanoic acid in the presence of few drops of cone. H₂SO₄ .
Or How are ester prepared?
When ethanoic acid reacts with ethyl alcohol in the presence of of cone. H₂SO₄, Ethyl ethanoate (ester) is formed. This reaction is called esterification.
CH₃COOH + CH₃CH₂OH ➡ConH₂SO₄ ➡ CH₃COOC₂H₅ + H₂O
Two carbon compounds ‘X’ and ‘Y’ have the molecular formula C₃H₆ and C₄H10 respectively. Which one of the two is most likely to show addition reaction? Justify your answer. Also give chemical equation to explain the process of addition in this case.
C₃H₆(Propene) show addition reaction because it is an unsaturated hydrocarbon.
CH₂ =CH—CH₃ + H₂ →Heat Ni →CH₃—CH₂—CH₃
Propene Propane
List four characteristics of homologous series.
a. All members have same general formula.
b. All members have same functional group.
c. Each successive member differ by —CH₂ unit.
d. All members are prepared by same methods.
Name the gas evolved when ethanoic acid is added to sodium carbonate. How will you test the presence of this gas.
When ethanoic acid reacts with sodium carbonate, carbon dioxide gas is liberated.
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
Test: Pass the gas through lime water. If lime water turns milky it shows the presence of CO₂ gas.
Write the names and molecular formulae of two organic compounds having functional group suffixed as ‘—oic acid’. With the help of a balanced chemical equation explain what happens when any one of them reacts with sodium hydroxide.
(i) Methanoic acid ➞HCOOH
(ii) Ethanoic acid ➞ CH₃COOH
HCOOH + NaOH ➞ HCOONa + H₂O
It is an acid-base reaction where sodium methanoate and H₂O is formed.
What happens when:
(i) Ethanol is burnt in air?
When ethanol is burnt in air CO₂ and H₂ O are formed.
CH₃–CH₂OH + O₂ → CO₂ + H₂O + heat and light
(ii) Ethanol is heated with excess cone. H₂ SO₄ at 443 K?
When ethanol is heated with excess of conc H₂SO₄ at 443 K gives ethene.
CH₃ CH₂ OH . ➡443K ConcH₂SO₄ ➡ CH₂ =CH₂ + H₂O
Write chemical equations to describe two different oxidations of ethanol.
1. Combustion : When ethanol burns in oxygen gives CO₂ and water
CH₃–CH₂OH + O₂ → CO₂ + H₂O + heat and light
2. Oxidation : When ethanol is heated with alkaline potassium permanganate or acidic potassium dichromate it oxidises in ethanoic acid.
CH₃ CH₂ CH₂ OH ➞ AlkalineKMnO₄ ➞ CH₃ CH₂ COOH+ H₂O
A compound X on heating with excess of cone. H₂SO₄ at 443K gives an unsaturated compound Y. X also reacts with sodium metal to evolve a colourless gas Z. Identify X, Y and Z. Write the equations of the chemical reaction of formation of Y and also write the role of conc.H₂SO₄ in the reaction.
CH₃ CH₂ OH . ➡443K/ConcH₂SO₄ ➡ CH₂ =CH₂ + H₂O
(X= Ethanol) (Y = Ethene)
2CH₃ CH₂ OH + 2Na ➡ 2CH₃CH₂ONa + H₂
(Z = Hydrogen)
Conc. H₂SO₄ acts as dehydrating agent.
You have three unlabelled test tubes containing ethanol, ethanoic acid and soap solution. Explain the method you would use to identify the compounds in different test tubes by chemical tests using litmus paper and sodium metal.
Solution Red Litmus Blue Litmus Na Metal
Ethanol    No change No Change H₂ gas
Ethanoic Acid:   No change Turns red H₂ gas
Soap solution     Turns blue No Change H₂ gas
A mixture of ethyne and oxygen is burnt for welding. In your opinion, why cannot we use a mixture of ethyne and air for this purpose?
A mixture of ethyne and air is not used for welding because when ethyne is burnt in air, it produces a sooty flame due to incomplete combustion which is not enough to melt metals for welding. While, if ethyne is burnt with oxygen, it produces a clean flame with high temperature due to complete combustion of ethyne which is enough to melt metals for welding.
State reasons to explain why covalent compounds: (i) are bad conductors of electricity? (ii) have low melting and boiling points?
(i) Covalent compounds do not dissociate into ions and hence cannot conduct electricity.
(ii) Covalent compounds have weak intermolecular forces of attraction, therefore, have low melting and boiling points.
Why should we prefer vegetable oils over animal fats for cooking food?
Animal fats generally contain saturated fatty acids which are harmful (Due formation of cholesterol) for health. Vegetable oils contain unsaturated fatty acids which are good for health. For this reason it is better to use vegetable oil for cooking
What will you observe on adding a 5% alkaline KMnO₄ solution drop by drop to some warm ethanol taken in a test tube? Write the name of the compound formed during the above chemical reaction. State the role of alkaline KMnO₄ solution in this reaction.
The purple colour of KMnO₄ decolourises and ethanoic acid will be formed
C₂H₅ OH ➡ .Alk KMNO₄ ➡ CH₂ COOH
Ethanol Ethanoic acid
Alk KMNO₄ acts as oxidising agent
What are hydrocarbons? Write the general formula of (a) saturated hydrocarbons (b) unsaturated hydrocarbons.
The chemical compounds which are made up of only carbon and hydrogen are called hydrocarbons. There are two types of hydrocarbon
General formula of saturated hydrocarbons : CₙH₂n₊₂
General formula of unsaturated hydrocarbons : Alkene-CnH₂n and Alkyne -CₙH₂n-₂
Why do soaps not form lather with hard water? Mention any two problems that arise due to the use of detergents instead of soaps.
Soap do not form lather with hard water, because hard water contains calcium and magnesium ions. These Ca²⁺ and Mg²⁺ ions react with soap to form precipitates which is insoluble in water
(i) Detergents are more expensive than soaps.
(ii) Some detergents are not biodegradable So they create pollution.
Unsaturated hydrocarbons show addition reactions but not saturated hydrocarbons. Why ?
Unsaturated hydrocarbons are more reactive due to the presence of double or triple bonds . These bonds are weaker than the single bond of saturated hydrocarbons. whereas saturated hydrocarbons are less reactive due to the presence of single bonds. These bonds are stronger than the double or triple bond of saturated hydrocarbons.Hence Unsaturated hydrocarbons show addition reactions but not saturated hydrocarbons
What would be the electron dot structure of a ‘molecule of sulphur which is made up of eight atoms of sulphur?
Compare the structures of benzene and cyclohexane by drawing them.

Benzene has 3 double bonds whereas cyclohexane has all single bonds.
What is meant by isomers? Draw the structures of two isomers of butane, C₄H₁₀.
Isomers are those compounds which have same molecular formula but different structural formula.
Butane have two isomers n-butane and iso-butane

n-butane iso-butane
Write the general formula of alkenes, and alkynes. Draw the structures of the first member of each series to show the bonding between the two carbon atoms.
Alkenes Cn H₂n
Ex. Ethene
C₂H₄

Alkynes Cn H₂n-₂
Ex. Ethyne
H-C ≡ C-H
How many structural isomers can you draw for pentane ?
Pentane has three structural isomers.
CH₃ —CH₂ —CH₂ —CH₂ —CH₃
Pentane (n-pentane)

2-Methyl butane(Iso-pentane)

neopentane (dimethylpropane).
Draw the structural formulae and electron dot structures of the possible isomers for the compound with molecular formula C₃H₆O
Or An aldehyde as well as ketone can be represented by the same molecular formula say C₃H₆O. Write their structures and name them. State the relationship between two in language of science.
Propanone Propanal

These are functional isomers.
Give the electron dot structure of chloro-methane. Also write the formula and the name of next homologue of it.

Next homologue

Chloromethane
A carbon compound X turns blue litmus to red and has a molecular formula C₂H₄O₂ . Identify X . Write the chemical equation of the reaction of X with the following:
(i) Sodium (ii) Sodium hydroxide, (iii) Ethanol.
X is ethanoic acid [CH₃ COOH]
(i) 2CH₃COOH + 2Na → 2CH₃COONa + H₂
(Sodium Ethanoate)
(ii)CH₃COOH + NaOH → CH₃COONa + H₂O
(Sodium Ethanoate)
(iii) C₂H₅OH + CH₃COOH ➞ Con H₂SO₄ ➞ CH₃COOC₂H₅ + H₂O
(Ethyl ethanoate)
Write three different chemical reactions showing the conversion of ethanoic acid to sodium ethanoate. Write balanced chemical equation in each case. Write the name of the reactants and products other than ethanoic acid and sodium ethanoate in each case.
(i) 2CH₃COOH + 2Na → 2CH₃COONa + H₂
(Sodium) (Hydrogen)
(ii)CH₃COOH + NaOH → CH₃COONa + H₂O
(Sodium hydroxide) (Water)
(iii) 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
(Sodium carbonate) (Water) (Carbon dioxide)
An organic compound ‘P’ is a constituent of wine. ‘P’ on reacting with acidified K₂Cr₂O₇ forms another compound ‘Q’. When a piece of sodium is added to ‘Q’ a gas ‘R’ evolves which burns with a pop sound. Identify P, Q and R and write the chemical equations of the reactions involved.
C₂H₅OH ➞ acidified K₂Cr₂O₇ ➞ CH₃COOH + H₂O
(P= Ethanol) (Q=Ethanoic Acid)
2CH₃COOH + 2Na → 2CH₃COONa + H₂
(Q=Ethanoic Acid) (R=Hydrogen)
Give a chemical test to distinguish between saturated and unsaturated hydrocarbons.
Saturated hydrocarbons do not react with bromine water and no color change whereas unsaturated hydrocarbons decolourise bromine water.
Saturated hydrocarbons burn with clean blue flame whereas
Unsaturated hydrocarbons burn with yellow sooty flame
Write any three physical properties and three uses of ethanol.
Properties
a. Ethanol is a liquid at room temperature
b. It is soluble in water.
c. It has burning taste.
Uses
a. Ethanol is a good solvent, so it is used in medicines like tincture iodine, cough syrupb.
b. It is used as an antiseptic.
c. Ethanol is an important component of all alcoholic drinks
The general formula of three compounds A, B and C is CnHn ₂ . ‘B’ has highest boiling point and ‘C’ has lowest boiling point.
(i) Mention the type of compounds A, B, C.
A, B, C are unsaturated compounds.
(ii) Which of these have minimum number of carbon atoms?
C has minimum number of carbon atoms.
(iii) Name the homologous series to which A, B and C belong.
They belong to alkene homologous series.
What is an oxidising agent? What happens when oxidising agent is added to propanol? Explain with the help of a chemical equation.
Substance which oxidizes other substances by giving them oxygen are called oxidising agent
Example : alkaline potassium permanganate or acidic potassium dichromate
When Propanol is heated with alkaline potassium permanganate or acidic potassium dichromate it oxidises in propanoic acid
CH₃ CH₂ CH₂ OH ➞ AlkalineKMnO₄ ➞ CH₃ CH₂ COOH+ H₂O
What are detergents chemically? List two merits and two demerits of using detergents for cleansing.
Detergents are generally sodium salts of sulphonic acids or ammonium salts of amines with chlorides or bromides ions.
Merits: (i) They are more effective than soaps.
(ii)They work well even with hard water.
Demerits:(i) Detergents are more expensive than soaps.
(ii) Some detergents are not biodegradable So they create pollution.
Convert CH₄ into CC1₄ by substituting hydrogen atom with chlorine atom in successive reactions.
CH₄ + Cl₂ →Sunlight → CH₃Cl + HCl
Chloromethane
CH₃Cl + Cl₂ →Sunlight→ CH₂Cl₂ + HCl
Dichloromethan
CH₂Cl₂ + Cl₂ →Sunlight→ CHCl₃ + HCl Trichloromethane
CHCl₃ + Cl₂ →Sunlight→ CCl₄ + HCl Tetrachloromethane
What is hydrogenation? What is its industrial application? State any one physical property of substances changes due to hydrogenation.
The addition of hydrogen to an unsaturated hydrocarbon to obtain a saturated hydrocarbon is called hydrogenation.
Or
Unsaturated hydrocarbons react with hydrogen in the presence of catalysts such as palladium or nickel to form saturated hydrocarbons. This reaction is called hydrogenation
Industrially, it is used to convert vegetable oils to vegetable ghee.
liquid unsaturated fatty acids are converted into solid saturated fatty acids.
Give reasons for the following:
(i) Diamond has high melting point.
Diamond has highest melting point because diamond have three dimensional structure and in diamond each carbon atom is bonded to four other carbon atoms with strong covalent bonds. it requires very high energy to separate the these atoms.
(ii) Graphite is good conductor of electricity.
in graphite, three valences of carbon are attached to three other carbon atoms, so due to the presence of free electrons, graphite is a good conductor of electricity
Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen is possible. State the essential conditions for an addition reaction. Stating this condition, write a chemical equation giving the name of the reactant and the product of the reaction.
Alkenes CnHn ₂ and Alkynes CnH₂n - ₂
In above two series of hydrocarbons, addition of H₂ is possible.
Essential condition
(i) Presence of catalysts such as palladium or nickel
(ii) The presence of multiple bonds (double and triple bonds) between carbon atoms
(iii) Heat
CH₂ =CH₂ + H₂ →Heat/ Ni →CH₃ —CH₃
Ethene Ethane
Carbon does not form ionic compounds, why?
Carbon needs to gain or lose four electrons to attain noble gas configuration.so that it would form ionic compound.
▶If the carbon atom gains four electrons, it is difficult for a nucleus with six protons to hold on to ten electrons.
▶ If the carbon atom loses four electrons, it requires a large amount of energy to remove four electrons.
Thus carbon doesnt form ionic compounds.
What are covalent compounds? Why are they different from ionic compounds?
Those compounds in which bonds are formed by sharing of electrons are covalent compounds. While ionic compounds are formed by complete transfer of electrons.
different between covalent compounds and Ionic compounds
1. Covalent compounds have weak intermolecular forces of attraction whereas ionic compounds have strong intermolecular forces of attraction.
2.Covalent compounds have low melting and boiling points whereas ionic compounds have high melting and boiling points.
3.Covalent compounds do not conduct electricity whereas ionic compounds conduct electricity in molten state or in aqueous solution.
Why is homologous series of carbon compounds so called? Write the chemical formula of two consecutive members of any two homologous series and state the part of these compounds that determines their (a) physical and (b) chemical properties.
Why is homologous series of carbon compounds so called because All the members of a series have the same functional group, similar structure and same general formula
(i) Homologous series of alcohol.
CH₃ OH Methanol
C₂ H₅ OH Ethanol
CH₃ - and C₂ H₅ - groups determine physical properties and - OH group determines chemical properties.
(ii) Homologous series of aldehyde.
CH₃ OH Ethanol
C₂ H₅ OH Propanal
CH₃ - and C₂ H₅ - groups determine physical properties while - CHO group determines chemical properties.
An organic compound “X’ on heating with con 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 compound ‘Z’ on combustion forms two molecules of CO₂ and three molecules of H₂ O. Identify giving reasons the compounds X’, ‘Y’ and ‘Z’. Write the chemical equations for all the chemical reactions involved.
CH₃ CH₂ OH . ➡443K/ConcH₂SO₄ ➡ CH₂ =CH₂ + H₂O
(X= Ethanol) (Y = Ethene)
CH₂ =CH₂ + H₂ →Heat/ Ni →CH₃ —CH₃
(Y = Ethene) (Z = Ethane)
2C₂ H₆ + 7O₂ ➞ 4CO₂ + 6H₂O + heat and light
(Z= Ethane)
On heating with con H₂SO₄, 'X’ dehydrates into ethene so ‘X’ is ethanol.
On addition of H₂, 'Y’ gives ethane so ‘Y’ is ethene.
On combustion, ‘Z’ gives 2CO₂ and 3H₂O so ‘Z’ is ethane.
In a tabular form, differentiate between ethanol and ethanoic acid under the following heads: (i) Physical state (ii) Taste (iii) NaHCO₃ test (iv) Ester test (v) Litmus test,
(i) Physical taste: Pure ethanol is a liquid at room temperature.
Pure ethanoic acid is solid below 290 K
(ii)Taste: Eathanol is bitter to taste
Ethanoic acid is sour to taste
(iii)NaHCO₃ test : Ethanol does not react with NaHCO₃.
Ethanoic acid reacts with NaHCO₃ and liberates CO₂
(iv)Ester test: Ethanol reacts with ethanoic acid to form easter
Ethanoic acid reacts with alcohol to form ester.
(v)Litmus test : Acetic acid turns blue litmus red
Ethanol oes not change colour of litmus
Soaps and detergents are both types of salts. State the difference between the two.
Soaps :
(i) The soaps are sodium or potassium salts of carboxylic acids( fatty acid).
(ii) The soaps contain —COONa group.
(iii) Soap is cannot be used in hard water
(iv) Soaps are biodegradable substances and do not harm nature.
Detergents :
(i) Detergents are sodium or potassium salts of sulphonic acids
(ii) Detergents contains —SO₃ Na or —SO₄ Na group.
(iii) Detergents work well even with hard water.
(iv) Detergents are non-biodegradable which are harmful for the environment.
Explain esterification reaction with the help of a chemical equation. Describe an activity to show esterification.
Esterification is the process in which carboxylic acid reacts with alcohol in presence of conc. H₂SO₄ to form pleasant fruity smelling compound ester. C₂ H₅ OH + CH₃ COOH ConcHSO ₂₄ CH₃ COOC₂ H₅ + H₂O
Exprement :
• Take 2 mL of ethanol in a test tube.
• Add 2 mL of glacial acetic acid.
• Add few drops of conc. H₂ SO₄ .
• Set the apparatus as shown in diagram.
• Heat the mixture in test tube in water bath for 5 to 10 minutes
Observation:
• Pleasant fruity smell is observed.
• Conclusion: Ester is formed.
Carboxylic acid (C₂H₄O₂) reacts with an alcohol in the presence of an acid catalyst to form a compound X. The alcohol on oxidation with alkaline KMnO₄ following by acidification gives the same carboxylic acid C₂H₄O₂ .Write the name and structure of (i) carboxylic acid, (ii) alcohol and (iii) the compound ‘X’.
C₂H₅OH + CH₃COOH ➞ Con H₂SO₄ ➞ CH₃COOC₂H₅ + H₂O
Ethanol Ethanoic acid Ethyl ethanoate.
CH₃CH₂CH₂OH ➞ AlkalineKMnO₄ ➞ CH₃CH₂COOH+ H₂O
Ethanol
(i) Carboxylic acid :
Name - Ethanoic acid
Structure :
(ii) Alcohol :
Name - Ethanol
Struture -
(iii) The compound ‘X’.
Name - Ethyl ethanoate
Struture -
Describe the cleaning process of soap and micelles
Or Explain the action of soap in removing an oily spot from a piece of cloth.
Cleaning Process of Soap and Micelle
Soap molecule has two dissimilar ends. At one end is the hydrocarbon chain which is non-polar and oil-soluble (hydrophobic) whereas at the other end is the carboxylate ion which is polar and water soluble (hydrophilic). Thus, a non-polar tail is soluble in oil/grease. whereas a polar head is water- soluble.
When soap is at the surface of water, its molecules arrange themselves in such a way that its ionic end is inside the water and the hydrocarbon tail is outside the water.
When a cloth with dirty spots is soaked with soap solution, the dirt dissolves in the hydrophobic end of the soap and culster of molecules are formed which is called a micelle. Soap in the form of a micelle is able to clean. because the oily dirt collected in the centre of the micelle. These micelles remain as colloidal solutions. Therefore, the dirt from the cloth is easily washed away
Complete the following chemical reactions and write the chemical name of the products formed.
(i) C₂ H₅ OH + O₂ ➞
C₂H₅OH + 3O₂ ➞ 2CO₂ + 3H₂O
(Carbon Dioxide)
(ii) C₂ H₅OH➞ 443K Conc H₂SO₄➞
C₂ H₅OH ➞ 443K Con H₂SO₄ ➞ CH₂ =CH₂ + H₂O
  (Ethene)
(iii) CH₃COOH +NaHCO₃ ➞
CH₃COOH + NaHCO₃ ➞ CH₃COONa + H₂O + CO₂
  (Sodium ethanoate)
(iv) CH₃COOC₂H₅ + NaOH ➞
CH₃ COOC₂H₅ + NaOH ➞ CH₃COONa + C₂H₅OH
  (Sodium ethanoate)
(v) C₂H₅OH + CH₃COOH ➞ Conc H₂SO₄➞
C₂ H₅OH + CH₃COOH ➞ Con H₂SO₄ ➞ CH₃COOC₂H₅
   (Ester)
(vi) CH₂ =CH₂ + H₂ ➞
CH₂ = CH₂ + H₂ ➞ CH₃– CH₃
(Ethane)
(vii) HCOOH + Na ➞
2HCOOH + 2Na ➞ 2HCOONa + H₂
  (Sodium methanoate)
(viii) C₂ H₅ OH ➞AlkMnO₄ ➞
C₂ H₅ OH ➞ AlkKMnO₄ ➞ CH₃ COOH + H₂O
  (Ethanoic Acid)