Carbon and its Compounds : Complete Set of Question



This set of questions contains all the possible concepts
which could be asked in the examination

Bonding of Carbon

Q.1 What is covalent bond and covalent compounds?

A chemical bond formed between two atoms by sharing of valence electrons so that each atom acquires the nearest noble gas electronic configuration is known as covalent bond and compound formed by the sharing of electrons are known as  covalent compounds. For e.g. formation of Methane (CH4)


Q.2  Why carbon forms covalent bonds?

To complete the octet, carbon can gain 4 electrons or lose 4 electrons. But if carbon gains electrons, it would be difficult for nucleus to hold 4 extra electrons as the carbon atom is very small in size. If carbon loses its electron, it would require a large amount of energy to remove 4 electrons as attraction force of nucleus is more in carbon atom. Thus, it is difficult for an atom of carbon to either gain or lose  electrons. So, carbon forms four covalent bonds and attains the noble gas configuration by sharing its valence electrons.


Q.3  What are the important properties of covalent compounds?

The important properties of covalent compounds are as follows:-

1. Covalent compounds are made up of molecules , not ions.

2. Covalent compounds have low melting and boiling point  because they have weak inter molecular forces.

3. Covalent compounds are bad conductors of electricity because they do not posses ions.

4. Covalent compounds are generally insoluble in water.


Q.4  Carbon is tetravalent. Explain?

Carbon atom has four valence electrons in its valence shell and it needs four more  electrons to complete its octet. Thus, carbon gets these electrons by mutual sharing d forms four covalent bonds. So, valency of carbon is four i.e. tetravalent (tetra = 4,valent = valency).These valencies are represented by four single lines, i.e.


Q.5  Draw the tetrahedral structure of carbon.

Carbon forms four covalent bonds and it does not lie in a plane but are directed towards the four corners of tetrahedron. The angle between two adjacent valencies is 109.5o known as tetrahedral angle.


Q.6  What is catenation?

Carbon has small size and carbon – carbon bond shows great strength so it has a   unique ability to combine with other carbon atoms to form long straight or branched chains and rings of different sizes. This ability of carbon is known as “Catenation”.

For e.g. Heptane(C7H16)


Q.7  How do carbon exist in nature?

Carbon occurs in two forms in nature:-

1. Free State : Carbon exists as free state in forms of Graphite, Diamond,

2. Combined State : Carbon combines with other elements to form compounds such as carbon dioxide (CO2), glucose (C6H12O6), sugar (C12H22O11) etc.


Q.7  What are the differences between ionic compounds and covalent compounds?

The major differences between ionic and cavalent compounds are as follows: -


Q.8  What is the difference between homoatomic and heteroatomic?

Molecules which consists of same kind of atoms are known as homoatomic molecules.e.g.H2, Cl2

Heteroatomic molecules consists of more than one type of molecules.e.g.NH3,CH4


Q.9  What would be the electron dot structure of carbon dioxide (CO2)?

Carbon dioxide is a compound consists of two oxygen atoms, covalently double bonded with a carbon atom.

Figure. Electron dot structure of CO2


Q.10  Draw the electron dot structure of a molecule of sulphur ( S8 ).

The atomic number of sulphur is 16.

So, its electronic configuration is

K       L       M

2        8        6

Thus, sulphur atom has 6 electrons in the valence shell. Therefore, it needs two more electrons to complete its octet and to acquire nearest noble gas electronic configuration. Thus, each sulphur atom shares its two electrons.

Figure :  Electron dot structure of octagonal S8 molecule


Q.11  Draw the electron dot structure of phosphorus ( P4 ) consists of four atoms.

The atomic number of phosphorus is 15.

So, its electronic configuration is

K       L       M

2        8        5

Thus, phosphorus has five electrons in the valence shell. Therefore, it needs 3 more electrons to complete its octet. Thus, phosphorus atom shares its three valence electrons, one each with three other phosphorus atoms.

Figure. Structure of P4 molecule


Q.12  Apart from the organic beings, where else do we find carbon? Mention the form in which it is available there and also its percentage.

Carbon is found in atmosphere and earth’s crust. Carbon is found as CO2 in atmosphere and as minerals in earth’s crust. The percentage of carbon in air is 0.03% and in earth’s crust about 0.02%.

 

Allotropy 

Q.13   What are allotropes?

The existence of different forms of an element which have different physical properties but their chemical properties are same are called allotropes and this phenomenon is known as allotropy. For e.g. carbon found in nature in three forms:-

1. Diamond   

2. Graphite  

3. Fullerenes


Q.14  What are the different properties and applications of diamond? Draw its   structure.

Diamond is a three dimensional network of strong carbon – carbon covalent bonds. The different properties of diamond are as follows : -

1. Due to the presence of large 3-D network of C - C covalent bonds, diamonds is very hard and have high melting point (around 4827o).

2. As all the 4 electrons are utilized in making covalent bonds, no free electron is available to conduct electricity and therefore, diamond is a bad conductor of electricity.

3. Diamond is transparent and shines in presence of light.

Figure : Tetrahedral arrangement of carbon atoms in diamond

Applications of diamond: -

1. Due to its hardness it is used in making cutting and drilling tools ( e.g.for cutting glasses).

2. Due to its brilliant shine it is used in making jewellery.

3. Diamond is used in surgical instruments to remove cataract from eyes.


Q.15 What are different properties and applications of graphite. Draw its    structure.

Graphite is a soft and layered structure. In graphite, each carbon atom is bonded with three other carbon atoms to form hexagonal rings. These hexagonal rings join together to form layers. These layers containing hexagonal rings are hold together by weak Vander Waal Forces. Due to weak Vander Waal forces, these layers can slide over each other.

Properties of Graphite:

1. Due to its layered structure, graphite is soft.

2. As the layers are bonded through weak Vander Waal forces it can act as a lubricant.

3. Due to presence of one free electron, it is a good conductor of electricity and heat.

Figure : Structure of graphite 

Applications of Graphite :

1. It is used in lead pencils as it is soft and leaves black mark on the paper.

2. Powered graphite is used as dry lubricant for machine parts which operate at high temperature where oil can’t be used because graphite is non volatile.

3. It is used in making electrode in the cells.

4. Graphite can be used as a dry lubricant for machine parts at high temperature.


Q.17 What are different properties and applications of fullerenes? Draw its structure.

Fullerene is a closed hollow cage in the form of sphere. It is composed of a sheet of linked hexagonal rings (each carbon atom is bonded with three other carbon atoms).Spherical fullerenes are usually called Buckyballs.C60 is the smallest fullerene molecule that forms the shape of a football.

Properties of Fullerene :

1. Fullerenes are stable, but not totally unreactive.

2. Fullerenes are soluble in many solvents like CO2 etc. But insoluble in other those have a small bond gap between the excited state and ground state.

3. Fullerenes are the only known allotrope of carbon that can be dissolved in common solvents at room temperature like C28, C36 etc.

Figure :  Structure of buck minster fullerene (C60

Uses of Fullerene:

1. Fullerene is used in making cosmetics.

2. Fullerene is used as a surface coating material to reduce friction.

3. Fullerene and its derivatives show antiviral activity which isused in drug delivery system.


Q.18 Diamond is poor conductor of electricity but graphite conducts electricity. Explain with reason

Diamond and graphite, both are forms of carbon having four valence electrons. In diamond, all four electrons forms covalent bonds, so no free electrons are available. Where as in graphite, three valence electrons forms covalent bond and remaining one electron is free to move and hence conduct electricity.


Q.19  What is the reason behind the soft and slippery nature of graphite?

The different layers of carbon atoms in graphite are held together by weak Vander Waals force of attraction and these layers can slide over each other and makes graphite soft and slippery.


Q.20  Give reason for the lustrous nature of diamond.

Diamond has high refractive index (around 2.42) which makes it transparent and lustrous.


Q.21  Why is fullerene so called ?

Fullerene resembles the framework of dome shaped halls designed by American architect Buckminster fuller so called as fullerenes.

 

Hydrocarbons and Nomenclature of Carbon

Q.22 What are hydrocarbons?

The organic compounds having carbon and hydrogen are known as hydrocarbons. The hydrocarbons can be classified as follows:-

(a) Saturated hydrocarbon - The saturated hydrocarbons are hydrocarbons in which carbon atoms are linked together by single bonds only.

For example :

(b) Unsaturated hydrocarbon - The hydrocarbons containing multiple bonds between two carbon atoms are called Unsaturated Hydrocarbons.

Unsaturated hydrocarbons can be further divided into two categories -

(a) Alkene : Hydrocarbons having at least one double bond between two carbon atoms are known as ‘alkene’.

For example:

(b) Alkynes : Hydrocarbons having at least one triple bond between two carbon atoms are known as ‘alkynes’.

For example :


Q.23 Draw the structure of ethyne.

In ethyne , two carbon atoms share three electron pairs and forms a triple bond. Each carbon atom shares one electron with each hydrogen atom to form carbon-hydrogen single bond.


Q.24  What are the possible structural isomers of hexane?

The possible structural isomers of hexane are as follows :-

                  


Q.25 What is homologous series?                                    

A series of organic compounds having same functional group and similar chemical properties in which the successive members differ by a – CH2 group is called a Homologous series. The members of homologous series are called homologues and phenomenon is called homology.


Q.26  What are the characteristics of homologous series?

The characteristics of homologous series are as follows :

1. All the members of a homologous series follow a general formula.

For example : 

All alkanes follow a general formula CnH2n+2.

All alkenes follow a general formula CnH2n.

All alkynes follow a general formula CnH2n-2.

2. Two successive members of a series differ by a “ – CH2” group.

3. All the members of a homologous series show similar chemical properties.

4. In a homologous series, the molecular mass of the members increases with increasing number of carbon atoms and the relative molecular mass of two immediate members differ by
14( CH2= 12 + 2 = 14)

5. Members of a homologous series show gradual change in their physical properties like boiling point, melting point, solubility etc.

6. All the members of the homologous series have similar chemical properties. The first member of the homologous series may differ in some chemical properties from the other members. 


Q.27  what are organic compounds?

Organic compounds are chemical compounds in which one or more atoms of carbon are linked with covalent bond with atoms of other elements.


Q.28 Give the structural differences between saturated hydrocarbons and unsaturated hydrocarbons with two examples each.

Saturated hydrocarbons contain only single bonds between any two carbon atoms where as unsaturated hydrocarbons contain at least one multiple bond (double bond or triple bond) between any of two carbon atoms along with single bonds.


Q.29   What is vital force theory?

Vital force theory is proposed by Berzelius in 1815.According to this theory, organic compounds are formed only under the influence of some mysterious force present in living organisms. This force is known as vital force. As mysterious force cannot be produced artificially so organic compounds can be only produced in the living organisms and not in the laboratory


Q.30 What are functional groups? Write the formula of the functional group present in alcohols, aldehyde, ketones and carboxylic acids.

Functional groups are specific groups of atoms or bonds within molecules that determines chemical properties (structures, properties and reactions) of any organic compounds.


Q.31  Draw the structure of the following compounds :               

(i)   Ethanoic acid     

(ii)  Bromopentane   

(iii)  Butanone  

(iv) Hexanal


Q.32  Draw the possible structural isomers of pentane.  

There are 3 possible structural isomers of pentane.


Q.33 Draw the structure of cyclopentane.


Q.34  What is the basic difference between saturated and unsaturated hydrocarbons when they get combust?

Saturated hydrocarbon shows complete combustion where as unsaturated hydrocarbon shows incomplete combustion. Due to higher content of carbon than hydrogen, unsaturated hydrocarbons burn with a sooty flame.

Chemical Properties of Carbon Compounds


Q.35 What is combustion? Give example.

Burning of carbon or its compounds in presence of oxygen is called combustion.

In combustion process, mainly two products are formed i.e. CO2 and H2O and energy is released in the form of heat and light.

For e.g. Methane ( natural gas ) burns in proper amount of oxygen to form carbon dioxide and water , and lot of heat also releases.


Q.36  What is the difference between complete and incomplete combustion?


Q.37  What is oxidation? Give examples.

Addition of oxygen to any substance is known as oxidation and substances which are capable to adding oxygen to other substances are known as oxidising  agents.

For e.g.

Carbon compounds get easily oxidized on combustion.

Alcohols undergo oxidation in presence of oxidizing agents like alkaline potassim permanganate (KMnO4) to form carboxylic acid.


Q.38    Define the term catalyst.

Catalyst is a substance that increases the speed of a chemical reaction without being used up in that particular reaction.


Q.39  What are addition reactions? Explain with examples.

The reactions in which two reactants combined to form a single product is called addition reactions. Unsaturated hydrocarbons contains double and triple bond and are more reactive so they form saturated hydrocarbons by addition of hydrogen. This process is known as hydrogenation. Only unsaturated hydrocarbons can show addition reactions.


Q.40  What are substitution reactions?Explain with examples.

The reactions in which one or more atoms of an organic molecule are replaced by some other atoms are called substitution reactions. These reactions are shown by saturated hydrocarbons only. Presence of  sunlight is necessary for these substitution reactions.


Q.41  What is composition of natural gas used for cooking ?

Natural gas is made up of methane (90%) and some amount of propane, butane and vapours of pentanes and hexanes.


Q.42  What is a flame ? Explain luminous and non-luminous flame ?

A flame is a region where burning of gaseous substances takes place.

1. Blue or non luminous flame : - In the presence of proper amount of oxygen, the fuel burns completely producing a blue flame. This type of flame does not produces light so flame is called as non-luminous. E.g., burning of LPG.

2. Yellow or luminous flame : -  When there is an insufficient amount  of oxygen,  the fuel burns incompletely and produces a yellow flame. This flame produces light so also called as luminous flame. E.g., burning of wax vapours.


Q.43  What are fossil fuels ?

Coal and petroleum are known as fossil fuels as they are former living things (plants, animals) preserved under the rocks.


Q.44  Why petro products causes pollution?

Petro products contain nitrogen and sulphur in small amounts and they can convert into their oxides and cause pollution.


Q.45 What is the difference between combustion and oxidation? Explain with example.

Oxidation is the process in which addition of oxygen or removal of hydrogen occurs.

For e.g., when ethanol reacts with oxygen , it produces CO2 and H2O.

However, when ethanol is heated with alkaline KMnO4 or acidified K2Cr2O7, it forms ethanoic acid.

Both these reactions are oxidation reactions because in both the cases oxygen has been added or hydrogen has been removed. The complete oxidation of an organic compound to form CO2 and H2O is called combustion. Therefore, oxidation of ethanol to form CO2 and H2O can also be called as combustion reaction while partial oxidation of a compound to give a compound other than CO2 and H2O is only known as oxidation.


Q.46  What are fuels?

Fuels are organic compounds which have stored energy in them and burn with heat and light


Q.47  What is a flame?

A flame is a region where combustion of gaseous substances occurs.


Q.48  What is the difference between non luminous and luminous flame?

Non-luminous flame is produced when oxygen supply is sufficient and the fuel burns completely with a blue flame where as luminous flame is produced when  insufficient amount of oxygen is present resulting in a yellow flame.

 

Important Carbon Compounds

Q.49 What are the physical properties of ethanol?

Ethanol is a colorless liquid with a pleasant smell and a burning taste.  It is soluble in water in all proportions. Its freezing point is 156 K and   boiling point is 351 K.


Q.50  What are the physical properties of ethanoic acid?

Ethanoic acid is acidic in nature with a pungent smell. It freezes at 290 K and boils at 391K.


Q.51  What are the applications of ethanol?

Some important application of ethanol are as follows:-

1. Ethanol is used as a solvent in different industries.

2. Spirit(ethanol 95%+water 5%) is used as an antiseptic to sterilize wounds and syringes in hospitals.

3. Ethanol is used in manufacturing of alcoholic beverages.

4. It is used as a fuel in cars along with petrol. This mixture of alcohol and  petrol is known as power alcohol.

5. Ethanol is used as an anti freeze in radiators of automobiles.

6. Ethanol is used as reagent for carry out organic reactions.


Q.52  What are the applications of acetic acid?

Some important applications of ethanoic acid are as follows:-

1. It is used in form of vinegar (5-8 % solution of acetic acid in water) as a preservative for food & pickles.

2. Acetic acid is used to form esters which are used in manufacturing of perfumes and scents.


Q.53  What is glacial acetic acid?

When pure ethanoic acid is cooled, it freezes to give a solid which looks like a glacier, due to which it is known as glacial acetic acid.


Q.54  What is denatured alcohol?

Denatured alcohol is the ethyl alcohol which is made unfit for drinking or misuse by adding small amounts of poisonous methanol, copper sulphate etc. Sometimes, a dye is also added to give it a blue color for the easy identification.


Q.55  What is power alcohol?

Power alcohal is a mixture of alcohol (100%) and petrol in proportion of  20:80.Power alcohal is used as a fuel in some countries.


Q.56  Explain the following reactions of ethanol.

(a)Combustion                     (b)Reaction with acid

(a) Combustion :-Ethanol undergoes combustion giving CO2 and H2O along with release of energy.

2C2H5OH    + 7O→   CO2 + 6 H2O  + Energy 

As ethanol gives only carbon dioxide (CO2) and water on combust with no other gas it is a cleaner fuel.

(b) Reaction with Metals :

Reaction of ethanol with metals shows its acidic nature. 


Q.57 How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties ?

(a)  Differences based on physical properties

• Smell- Ethanoic acid has a pungent smell where as ethanol has a pleasant smell.

• Melting point- Ethanol has lower melting point (156 k) than ethanoic acid (290 K).

• Physical state- Ethanoic acid is solid (glacial acetic acid) in winters where as ethanol is a liquid.

(b)  Differences based on chemical properties

(i) Ethanoic acid react with sodium hydrogen carbonate and  carbon dioxide gas is evolved with effervescence. However, ethanol do not show such reaction.

(ii) Reaction with caustic alkalies- Ethanoic acid reacts with both sodium hydroxide (NaOH) and potassium hydroxide (KOH) to form corresponding salt and water. Ethanol do not show such reaction


Q.58 An organic compound ‘A’ is a constituent of wine or beer. This compound, on heating with alkaline KMnO4 or acidified K2Cr2O7, gives another organic compound ‘B’ which turns blue litmus paper into red. Find  the compound ‘A’. Write chemical equation of the reaction that takes place to form the compound ‘B’.Find the compound ‘B’.

(i) As organic compound ‘A’ is a constituent of wine or beer, it must be ethanol(CH3CH2OH).    

(ii) Ethanol on oxidation gives ethanoic acid ( CH3COOH) which turns blue litmus red, thus compound B must be ethanoic acid.


Q.59 An organic compound A of molecular formula C2H6O, on oxidation with potassium dichromate and sulphuric acid, gives an acidic compound B. The compound A reacts with B on warming in the presence of conc. H2SO4 to give a sweet smelling substance C. Identify A, B and C.

Given,

• Since B is an acid which on heating with A in presence of a few drops of conc. H2SO4 gives a sweet smelling compound C, therefore, C must be an ester and A must be an alcohol.

• Since A is an alcohol with Molecular Formula C2H6O, it must be ethanol (CH3CH2OH).

• Since ethanol (A) on oxidation with K2Cr2O7/H2SO4 gives an acid (B), therefore, acid (B) must be ethanoic acid.

•  If A is ethanol and B is ethanoic acid then C must be ethyl ethanoate.

All the reactions involved in the above question are as follows :

Soaps and detergents


Q.60  What is a soap?

A soap is the sodium or potassium salt of a long chain fatty acids such aspalmitic acid, stearic acid oleic acid etc which has cleansing properties in    water.

For e.g.Sodium sterate,C17H35COONa.


Q.61 What is a detergent?

Detergents are sulphonate or ammonium salts of long chain sulphonic acids and has cleansing properties in water.

For e.g.Sodium-n-dodecyl sulphate


Q.62  Explain the preparation method of soap.

The soap is generally prepared by heating animal fats or vegetable oils with sodium hydroxide or pottasium hydroxide. This process of formation of soap by hydrolysis of fat or oil with base is known as saponification. 


Q.63  What is cause behind hardness of water?

The hardness of water is because of the presence of bicarbonates, chlorides and sulphates of calcium and magnesium.


Q.64  Explain why detergents are better cleansing agents than soaps in hard water?

Hard water contains calcium and magnesium ions. These ions react with soap and form a precipitate of calcium and magnesium salts of fatty acids which    produces an insoluble residue on fabrics. Due to precipitation, lot of soap is wasted. Where as in detergents, calcium and magnesium salts are soluble in water and can be used even in hard water. Thus detergents are better cleansing agents than soaps in hard water.


Q.65  State in brief the action of soaps in removing an oily spot from a fabric.

Soaps consist of a large hydrocarbon tail which is hydrophobic (water or water repelling) with a negatively charged head which is hydrophilic (water-loving).

Soap of Detergent Molecule 

When soap is dissolved in water, the molecules associate together as clusters called micelles in which, water molecules being polar in nature, surrounds the ions and the hydrocarbon part of the molecule attracts grease, oil and dirt.


Q.66  Write down one disadvantage of detergents.

The one of the disadvantage of detergent is that some of the detergents are not biodegradable i.e. they cannot be decomposed by microorganisms. Thus, detergent causes water and soil pollution.


Q.67  What are the differences between soaps and detergents?


Q.68 Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents like ethanol also?

A soap molecule has two ends which have different properties. The hydrocarbon part of soap molecule is soluble in oil or grease and attach to the grease or oil particles present on dirty clothes. Whereas, the ionic part of soap molecule is soluble in water and can attach to water particles. As a result, spherical ionic micelles are formed. Because hydrocarbon chain of soap is soluble in ethanol, therefore, micelle formation does not takes place.


Q.69  What change will you observe if you test soap with litmus paper (red or blue)?

Soap is alkaline in nature and hence turns red litmus paper blue.


Q.70 What is micelle?

Micelle is spherical aggregate of soap molecule in the soap solution in water.


Q.71 How soap molecules are arranged in a soap micelle?

In soap micelle, hydrocarbon ends directed towards the center and ionic ends directed outwards.


Q.72  What is scum?

When soap is dissolved in hard water then a curdy white precipitate forms, which is known as scum.

 

Value Based Questions : -

Q.1 Cough syrups and some other some other syrups contain alcohol in high amount. Some people have the habit of drinking alcohol. The alcohol addict people have started using cough syrups which contain alcohol and cause addiction. To resolve this problem, government is planning to ban cough syrups.

(a) What is alcoholic beverage?

(b) Should manufacturing of cough syrups be stopped?

(c) How can we make people aware of harmful effects of consuming cough syrups unnecessarily?

(a) An alcoholic beverage is a drink containing ethanol (C2H5OH), commonly known as alcohol.

(b) Syrups give instant relief and it is easy to use so its manufacturing  should not be stopped.

(c) The warning should be stated on its bottles and posters should be pasted at important place that cough syrups are harmful if taken in excess.


Q.2 Petrol products are in great demand as vehicles are increasing day-by-day. Our natural resources are limited. Car-pooling can also help i.e., people going to same destination can go together and share expenses of fuel. Ethanol can be mixed with petrol to reduce pollution.  

(a) How do we get petro-products?

(b) How can we make people aware that petro-products should be used judiciously?

(c) What value is involved in car-pooling?

(d) How can we reduce air pollution?

(a) Petro products are substances derived from crude oil (petroleum) after being processed in oil refineries.

(b) By posting posters and organizing awareness rallies around the city.

(c) Sharing, caring and conservation of natural resources.

(d)  (i) Using bicycles for short distances.

       (ii) Promoting car pooling.


Q.3 Ice creams and candies contain artificial flavors made up of esters. It also contains cream and lot of sugar. Excess of sugar produces acid which causes tooth problems. Children love ice creams and candies without thinking about its adverse effects. It results obesity. Children should take more milk, fruits, and green leafy vegetables.

(a) What is an ester?

(b) Why should sugar intake be reduced?

(a) Esters are pleasant fruit –smelling compounds formed by the reaction of carboxylic acids and alcohols.  

(b) Excess of sugar intake causes problems like cavities, diabetes and obesity so it should be reduced.



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