JKBOSE 10th Class Science Solutions Chapter 8 Carbon And Its Compounds

◆ Carbon is a versatile element that forms the basis for all living organisms and many things which we use in our daily life.

◆ Chemical bond is the attractive forces which hold the atoms or ions together in a chemical species.

◆ Causes of chemical bonding (i) the tendency of the atoms of the various elements to acquire the stable nearest noble gas configuration i.e., to complete their octet and (ii) to acquire a state of minimum energy.

◆ During the formation of a chemical bond, energy is given out.

◆ Noble gases are chemically less reactive and have eight electrons in their valence shells (except helium).

◆ Octet rule is the tendency of an atom of the element to have eight electrons in its valence shell.

◆ Molecule is an electrically neutral cluster of mutually bonded atoms. e.g. CH₄, NH₃, H₂O etc.

◆ Chemical bonds are mainly of three types (a) Ionic or electrovalent bond (b) Covalent bond (c) Co-ordinate bond. “

◆ Covalent bond. It is the bond formed by equal contribution and mutual sharing of electrons between two atoms so that both the atoms get their octet (or duplet) complete.

◆ Covalent compounds. The compounds containing covalent bonds are called covalent compounds.

◆ Covalency. It is the number of electrons contributed by an atom of the element for mutual sharing during the formation of a covalent bond.

◆ Bond pair of electrons is the pair of electrons shared between two atoms.

◆ Lone pair of electrons is the electron pair present on one atom which does not take part in sharing.

◆ Single, double and triple bonds are formed by the mutual sharing of one, two and three electron pairs between two atoms.

◆ Organic Compounds. These are made of C, H, O, N, S, P, halogens and have covalent bonds. Or The organic compounds include hydrocarbons and their derivatives.

◆ Catenation. It is the property by virtue of which atoms of the same element get linked together through covalent bonds so as to form long straight, branched or closed chains or rings. For example, carbon atom shows catenation to maximum extent.

◆ Tetracovalency or Tetravalency. Carbon atoms shows tetracovalency because it has four electrons in its valence shell.

◆ This large variety of compounds is formed by carbon because of its tetravalency and the property of catenation.

◆ Structural formula. It gives us t the relative arrangements of bonded atoms in a molecule.

◆ Functional group. An atom o or group of atoms or some other characteristics structural feature which when present, in a molecule gives some special properties to a compound e.g., OH alcoholic group, – CHO aldehydic group. J

◆ Homologous series. It is a series of compounds having similar structural formulae, same functional group and hence, similar chemical properties.

◆ IUPAC System stands for International Union of Pure and Applied Chemistry System.

◆ Saturated hydrocarbons are those compounds which contain C – C single bonds in their molecules.

◆ Unsaturated hydrocarbons. They include alkenes and alkynes. These are those compounds which contain C = C bonds or C ≡ C bonds in their molecules.

◆ Pyrolysis. It is decomposition of higher molecular weight hydrocarbons into lower molecular weight hydrocarbons on heating to a high temperature in the absence of air.

◆ Isomerism. The compounds having same molecular formula but different properties are called isomers and this phenomenon is called isomerism.

◆ Carbon and its compounds are some of our major source of fuels.

◆ Ethanol and ethanoic acid are carbon compounds of importance in our daily lives.

◆ The action of soaps and detergents is based on the presence of both hydrophobic and hydrophilic groups in the molecule and this helps to emulsify the oily dirt and hence remove it from clothes.

⇒ Hydrocarbons. These are the covalent compounds of carbon and hydrogen.

⇒ Organic Chemistry. It is the study of hydrocarbons and their derivatives.

⇒ Allotropy. It is the phenomenon of existence of an element in different forms having different physical properties but same or slightly different chemical properties.

⇒ Alkanes. These are the hydrocarbons containing C- C and C H single bonds. These are also called saturated hydrocarbons. General formula of alkanes is C_nH_{2n + 2} n = : 1, 2, 3………

⇒ Unsaturated Hydrocarbons. These are the hydrocarbons containing C = C or – C ≡ C- bonds in their molecules.

Ans. :Ö::C::Ö:

Ans. Pentane has three structural isomers.

These are

Ans. These are 1. Tetracovalency 2. Catenation.

Ans. Formula of cyclopentane is C₅H₁₀ and its electron dot structure is :

(a) Ethanoic acid

(b) Butanone

(c) Bromopentane

(d) Hexanal.

Are structural isomers possible for bromopentane ?

Ans. (a) Ethanoic acid has structure

(c) Bromopentane. There are three structural isomers possible for bromopentane. These are

CH₃ – CH₂ – CH₂ – CH₂ – CH₂ – CHO –

Ans. (a) Bromoethane

(b) Methanal Saistige

(c) Hex-1-yne.

Ans. This is because in this reaction oxygen gets added to ethanol.

Ans. A mixture of ethyne and air is not burnt for welding. This is because air also contains nitrogen along with oxygen. Nitrogen will also burn in oxygen producing oxides of nitrogen such as nitrous oxide (NO) and nitrogen dioxide (NO₂) which cause pollution.

Ans. The following two tests are used :

1. Litmus test. Treat the given compound with blue litmus solutions. If the blue litmus solution turns red, it is a carboxylic acid and if does not turn red, it is an alcohol.

2. Sodium bicarbonate test. Add some sodium bicarbonate solution to the given compound. If their is a brick evolution of a colourless and odourless gas (CO₂) which turns freshly prepared lime water milky, it is carboxylic acid and if their is no effervescence, it is an alcohol.

Ans. The substances which can oxidise other substances by giving oxygen are called oxidising agents.

Examples. Alkaline potassium permanganate solution, acidified potassium dichromate solution etc.

Ans. No, we can’t check whether the water is hard or soft using a detergent.

Ans. This is because when soap molecules dissolve in dirt, the dirt is somewhat loosened from the clothes and in order to remove it from clothes, the clothes have to be beaten on a stone or beaten with a paddle or scrubbed with a brush or mixture has to be agitated in washing machines.

(a) 6 covalent bonds

(b) 7 covalent bonds

(c) 8 covalent bonds

(d) 9 covalent bonds.

Ans. (b).

(a) carboxylic acid

(b) aldehyde

(c) ketone

(d) alcohol.

Ans. (c).

(a) the food is not cooked completely

(b) the fuel is not burning completely

(c) the fuel is wet

(d) the fuel is burning completely.

Ans. (b).

Ans. The formation of CH₃Cl can be represented as :

Carbon forms single covalent bonds with three H-atoms and one Cl-atom by sharing one electron pair with each C-H bonds are non-polar. But C-Cl bond is polar this is because C and H leave almost same electronegativity whereas Cl has more electronegativity than carbon.

Ans. (a) Ethanoic acid

Ans. A series of compounds having similar structural formulae, same functional group and hence similar chemical properties is called a homologous series. In the homologous series any two adjacent members differ by CH₂ unit in their molecular formulae.

For example homologous series of aldehydes (or alkanals) can be represented as:

H – CHO                                         Methanal

CH₃ – CHO                                     Ethanal

CH₃ – CH₂ – CHO                           Propanal

CH₃ – CH₂ – CH₂ – CHO                 Butanal

CH₃ – CH₂ CH₂ – CH₂ – CHO         Pentanal and so on.

Ans. Distinction between ethanol and ethanoic acid :

Ans. Soap molecule has two ends, one is hydrophillic, and it dissolves in water, while the other end is hydrophobic, and it dissolves in hydrocarbons. When soap is at the surface of water, the hydrophobic tail of soap will not be soluble in water and the soap will align along the surface of water with the ionic end in water and the hydrocarbon ‘tail’ pointing out of water. Inside water, these molecules have a unique orientation which keeps the hydrocarbon portion out of the water. This is achieved due to the formation clusters of molecules in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. This formation is called a micelle.

Ans. Soap solution will turn red litmus paper blue because soap is alkaline in nature.

Ans. The addition of hydrogen to unsaturated hydrocarbons in the presence of catalysts like palladium, platinum, nickel etc. to give saturated hydrocarbons is called hydrogenation.

This reaction is used for hydrogenation of liquid vegetable oils using a nickel catalyst to get artificial or vanaspati ghee.

Ans. Out of C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH₄; C₃H₆ and C₂H₂ undergo addition reactions because they contain multiple bonds.

Ans. Distinction between Butter and Cooking oil :

Soap are sodium or potassium salts of higher fatty acids e.g. sodium palmitate, C₁₅H₃₁COO^–Na⁺, sodium stearate, C₁₇H₃₅COO^–Na⁺ etc. A molecule of soap consists of two parts:

(a) a long chain hydrocarbon part (C₁₅H₃₁ –, C₁₇H₃₅ …. etc.) which is soluble in oil and (b) ionic part on polar group, – COO^–Na⁺ which is soluble in water. Thus a molecule of soap can be represented as :

The long hydrocarbon chain is insoluble in water but soluble in oil and greases whereas the ionic or polar part is soluble in water. The dirty clothes contain greasy and oily substance (dirt). Soap molecules dissociate in water to g give carboxylate ion (RCOO^–) and cation (Na⁺). When soap is added to dirty clothes dipped in water, the hydrocarbon part of carboxylate group dissolving in greasy or oily dirt particles where the polar (COO^–) group remain attached to water. In this way each oil droplet acquires negative charge. These negative charged oil droplets called micelles can not associate and hence form a stable emulsion water. These small droplets along with dirt can be easily washed away with water by agitating the mixture of soap and water. Thus the soap helps in removing greasy dirt by producing a stable oil in water type emulsion. Also the soap reduces surface tension of water. Hence cloth is wetted more effectively and is cleaned. Agitation of mixture of soap and water is necessary to remove small droplets or micelles.

Ans. (a) Covalent bond. The bond formed by equal contribution and mutual sharing of electrons between two atoms (same or different) so that both the atoms acquire the stable nearest noble gas configuration i.e. get their octet complete is called covalent bond.

The mutually shared electrons become the common property of both the bonded atoms.

The number of electrons contributed by an atom of the element for mutual sharing during the formation of a covalent bond is called its covalency.

Each pair of shared electrons is represented by putting a single line (—) between two atoms.

In the example given below :

Examples. (i) Formation of a hydrogen molecule (H₂). At. no. of hydrogen = 1. It has one electron in the first orbit. When two hydrogen atoms approach each other they share their single electron present in their first orbits. Each hydrogen atom can now be thought of as having noble gas configuration of helium. It may be represented as:

(ii) Formation of chlorine molecule. In this case, both the chlorine atoms have seven electrons in their outermost shell and they contribute one electron for mutual each to form a covalent bond. Thus, both the chlorine atoms acquire noble gas configuration of argon. This may be depicted as :

(iii) Formation of HCI molecule. Hydrogen atom has only one electron and chlorine atom has seven electrons in its valence shell. Therefore, by mutual sharing of electron pair between a hydrogen and a chlorine atom both the atoms acquire nearest noble gas configuration. Hydrogen atom acquires electronic configuration of helium where as chlorine atom gets electroric configuration of argon.

(b) Multiple covalent Bonding. If the two atoms share one electron pair, bond is known as single covalent bond and is represented by one dash (—). If the two atoms share two electron pairs, bond is known as double covalent bond and is represented by two dashes (=). If the two atoms share three electron pairs, bond is known as triple covalent bond and is represented by three dashes (≡).

In the case of H₂, Cl₂ and HCI molecules (given above) there are single bonds between the atoms.

Formation of Double Bond. Two oxygen atoms combine to form an oxygen molecule by sharing two electron pairs. In the formation of oxygen molecule, each oxygen atom has six electrons in the valence shell and require two electrons to complete the octet. Therefore, both the atoms contribute two electron pairs are shared and hence there is a double bond between the oxygen atoms. The covalency of oxygen is two.

Formation of Triple Bond. In the formation of a nitrogen molecule, each of the bond nitrogen atoms having five electrons, provides three electrons to form three electrons pairs for sharing. Thus, a triple bond is formed between the two atoms. Here, covalency of nitrogen is three.

Ans. (a) Covalent bonds in methane (CH₄) molecule. The atomic number of carbon is 6. Its electronic configuration is 2, 4. This means that carbon atom has four valence electrons. These are shared by the electrons of four hydrogen atoms. As a result, the carbon atom gets linked to four hydrogen atoms by four covalent bonds. The formation of methane molecule may be shown as follows:

(b) Covalent bonds in carbon tetrachloride (CCl₄) molecule. The atomic number of carbon is 6. Its electronic configuration is 2, 4. The four electrons present in the valence shell of carbon atom are shared by the unpaired electrons of four chlorine atoms (2, 8, 7). Thus, carbon atom gets linked to four chlorine atoms by four covalent bonds. The formation of carbon tetrachloride molecule may be shown as follows:

(c) Covalent bonds in water (H₂O) molecule. The atomic number of oxygen is 8. Its electronic configuration is 2, 6. This means that oxygen atom has six valence electrons. In order to have eight electrons in its valence shell oxygen atom shares two electrons with the electrons of two hydrogen atoms. Thus, oxygen atom gets linked to hydrogen atoms by two covalent bonds. The formation of water molecule may be shown as below:

(d) Covalent bonds in ammonia (NH₃) molecule. The atomic number of nitrogen is 7. Its electronic configuration is 2, 5. Nitrogen atom has five valence electrons. In order to have eight electrons in the valence shell, the nitrogen atom shares three electrons with the electrons of three hydrogen atoms. Thus, nitrogen atom gets linked to three hydrogen atoms by three covalent bonds. The formation of ammonia molecule may be shown as follows:

(e) Covalent bonds in ethylene (C₂H₄) molecule. Ethylene molecule has two carbon atoms. Each carbon atom shares two electrons with the two hydrogen atoms. At the same time, both the carbon atoms mutually share two electrons each. Thus both the carbon atoms get linked by double bond. Each carbon atom also gets linked to two hydrogen atoms by single bonds. The formation of ethylene molecule may be shown as follows:

(f) Covalent bonds in carbon dioxide (CO₂) molecule. Carbon atom has four electrons. Each oxygen atom has six valence electrons (2, 6). The carbon atom shares its electrons with the electrons of the two oxygen atoms. As a result, the carbon atoms get linked to the oxygen atoms by double bonds. The formation of carbon dioxide molecule may be shown as follows:

Ans. Some important chemical properties of carbon compounds are :

1. Combustion. The carbon compounds on burning in a free supply of air or oxygen produce carbon dioxide, water and a large amount of heat and light energy.

Saturated hydrocarbons generally burns with a clean flame whereas unsaturated hydrocarbons burn with a yellow flame and produce a large amount of black smoke. Also the saturated hydrocarbons also burn in the limited supply of air with a sooty flame. 2. Addition reactions. The chemical reactions in which two reactant molecules get added to form a single molecule are called addition reactions. During the addition reaction one of the reactant molecules must contain a multiple bond.

Unsaturated hydrocarbons (alkenes and alkynes) undergo addition reactions.

The above reaction is also called catalytic hydrogenation. This reaction is used for the hydrogenation of liquid vegetable oils from liquid vegetable oils (which are long unsaturated hydrocarbon chains)

                 

(c) Oxidation. In addition to combustion (which involves oxidation) carbon compounds also undergo oxidation reactions.

Examples. Alcohols are oxidised to aldehydes and ketones. The aldehydes and ketones are further oxidised to monocarboxylic acids.

(d) Substitution reactions. These reaction involve the replacement of an atom or group of atoms from a molecule by another atom or group without any change is structure in remaining part of the molecule.

Saturated hydrocarbons undergo substitution reactions.

Examples:

Another example is from allyl halide which also undergo substitution reactions

Ethanol	Ethanoic acid
1. It has a typical alcoholic smell. 2. It has burning taste.	1. It has vinegar-like smell. 2. It has sour taste.

Ethanol	Ethanoic acid
1. It has no action on litmus paper. 2. It has no action with sodium bicarbonate.	1. It turns blue litmus solution red. 2. It decomposes sodium bicarbonate producing carbon dioxide.

Ans. The important characteristics of covalent compounds are as given ahead :

1. Covalent compounds consist of molecules. Covalent compounds do not have any ions. Therefore, they consist of molecules. For example, H₂, Cl₂, H₂O, NH₃ etc.

2. Covalent compounds are liquids or gases in nature. Only a few covalent compounds are solids (e.g. sugar, glucose, iodine). These are mostly liquids (water, ethyl alcohol) or gases (oxygen, hydrogen, ammonia) at room temperature. Actually, the attractive forces in covalent molecules are weak and these molecules are not as close to one another as the ionic solids.

3. Covalent compounds have low melting and boiling points. As covalent molecules do not have ions, the attractive forces among them are weak. Therefore, the covalent molecules can be easily separated from each other. In other words, they have low melting and boiling points.

4. Covalent compounds do not conduct electricity. Covalent compounds normally do not conduct electricity. Some of them are poor conductors of electricity. The current is carried by the ions. As covalent compounds do not have ions, these are poor conductors of electricity.

5. Covalent compounds are insoluble in water. Covalent compounds generally do not dissolve in water. They are soluble in alcohol, ether, benzene etc. which are called organic solvents. However, some of them such as ammonia and ethyl alcohol are water soluble.

Ans. Soaps are sodium or potassium salts of higher fatty acids. When the naturally occurring esters called fats or oils are heated with NaOH solution, they undergo hydrolysis to form sodium salt of higher fatty acid (called soap) and glycerol.

Preparation of soap. Heat fat or oil with sodium hydroxide solution. After a few minutes, and constant stirring, the oil and water layers get mixed.

Add 5-10 g of common salt to it, stir the mixture and allow it to cool. On cooling pale yellow a solid forms as a cake called soap.

The same principle is used for making soap in soap industry. Some other substances like perfumes, disinfectants and medicines are added to soap to give it desired characteristics.

1. The first member of alkanal series is ………….. .

2. Formation is an aqueous solution of ………….. .

3. Fermentation of sugar gives ………….. .

4. IUPAC name of (CH₃)₃ COH is ………….. .

5. The IUPAC name of acetone is ………….. .

6. The IUPAC name of formic acid is ………….. .

7. The organic acid obtained from vinegar is ………….. .

8. ………………. are used for making artificial perfumes.

9. Organic acids turn …………….. litmus solution ………….. .

10. The functional group present in ethanol is ………….. .

Ans. 1. Methanoic acid 2. Methanol 3. ethanol 4. 2-methyl propan-2-ol 5. Propanone 6. methanoic acid 7. Acetic acid 8. Esters 9. blue, red, 10. hydroxyl (-OH)

Ans. Substitution reactions. These are the reactions in which one or more H-atoms of a molecule are replaced by corresponding number of other atoms or groups.

Methane reacts with chlorine in the presence of sunlight to form chloromethane and hydrogen chloride

Addition reactions. These are the reactions in which an unsaturated hydrocarbon combines with another substance to give a single product.

Ethane reacts with hydrogen when heated in the presence of nickel catalyst to form ethane.

Ans. The two properties of carbon which lead to a huge number of carbon compounds are :

(a) Catenation. It is the property of carbon due to which a large number of carbon atom link among themselves to form long straight or branched or of different lengths. Also carbon atoms may be linked by single, double or triple bonds.

(b) Tetracovalency. Carbon shows tetracovalency. It requires 4 electrons to become stable. Therefore carbon can form four covalent bonds with carbon or some other atom. Such as hydrogen, oxygen, nitrogen, sulphur, halogen etc. This further increases the number of compounds of carbon.

(i) Saponification. It is the process of alkaline hydrolysis of fat to give soap and glycerol.

(a) Ethanol to ethane

(b) Propanol to propanoic acid. Ans.

1. It is a colourless liquid.

2. It is soluble in water.

3. It produces hydrogen with sodium metal.

2C₂H₅OH + 2Na → 2C₂H₅O-Na⁺ + H₂

4. It forms an ester with acetic acid.

1. It is a colourless liquid.

2. It has vinegar-like smell.

3. It is soluble in water.

4. It forms an ester with ethyl alcohol.

5. It produces hydrogen with sodium. 2CH3COOH + 2Na

2CH₃COO + 2Na → 2CH₃COONa + H₂

6. It turns blue litmus solution red.

(a) Ethanoic acid

(b) Propanone

(c) Hexanol

1. It is a colourless liquid having a sour taste.

2. It has vinegar-like smell.

3. It boils at 391 K and freezes at 290 K.

4. It is miscible with water in all proportions.

1. Esterification. When an acid is heated with an alcohol in the presence of conc. H₂SO₄ an ester is produced. This is a slow reversion reaction and is called esterification.

Esters are sweet-smelling substances.

                     

3. Action with carbonates and bicarbonates. Ethanoic acid decomposes carbonates and bicarbonates producing salt, carbon dioxide and water.

2CH₃COOH + 2Na ↓ 2CH₃COONa+ H₂

(i) 1-Butene

(ii) 2-Iodopropane

(iii) 2-Propanol

(iv) Butanoic acid

(v) 3-Pentanone.

(i) It is colourless liquid having typical alcoholic smell.

(ii) It has burning tast.

(iii) It is soluble in water.

(i) It has no action on litmus paper.

(ii) It has no action with sodium bicarbonate.

(iii) On heating with sodium metal, it gives colourless and odourless hydrogen as :

(iv) On heating with acetic acid, it forms ester having fruity smell.

(a) Two atoms of the same element combine to form a molecule. The bond between them is known as ……………… bond.

(b) In the formation of oxygen molecule, the oxygen atoms share …….. electrons each.

(c) The number of single covalent bond in the molecule of ammonia is ………………

Ans. (a) covalent (b) two (c) three.

Ans. When ethanol reacts with ethanoic acid on warming with conc. H₂SO₄, sweet smelling ester is formed.

The name of the product is ethyl ethanoate.

Ans. A covalent bond is formed by the sharing of electrons between the atoms. The bonds are represented by dashes (-) and are directional in nature. The directional nature of the covalent bonds gives covalent molecules having two or more such bonds of a definite shape. This is also called definite geometry of the covalent molecule. Thus, the geometry of a covalent molecule may be defined as the arrangement of the different atoms with respect to each other.

Ans. The carbon compounds are being increasingly used as a source of energy, as medicines, colours, textiles, plastics, food preservatives etc.

(a) detect the presence of ethanol.

(b) show that methanal contains an aldehyde group.

Ans. (a) Warm the compound with ethanoic acid and a few drops of conc. H₂SO₄. A sweet smell (due to the formation of ester) indicates the presence of ethanol.

(b) Methanal gives silver mirror test with Tollen’s reagent. This shows that methanal contains aldehydic group.

Ans. Allotropy. When an element exists in more than one form having different physical properties but same or slightly different chemical properties, the various forms are called allotropic forms or allotropes and this phenomenon is called allotropy.

The element like carbon, sulphur, phosphorus etc show allotropy.

The three allotropic forms of carbon are:

(i) Diamond (ii) Graphite (iii) Fullerenes.

Ans. The structure of diamond is as shown below :

In diamond, each carbon atom is bonded to four other carbon atoms by covalent bonds resulting in the formation of a three dimensional network structure.

Due to the presence of strong covalent bonds, diamond is hard and has high melting point.

Ans. The structure of graphite is as shown below :

In graphite each C-atom is bonded to three other carbon atoms to four hexagonal rings which are held together by weak van der Waals forces of attraction. Therefore, graphite has a two dimensional sheet like structure.

Due to the presence of one free electron left with each C-atom, graphite is a good conductor of electricity.

Ans. Fullerenes are also allotropes of Carbon, for example, the fullerene, C60 has carbon atoms arranged in the form of a football and it looked like the geodesic dome designed by the US architect Buckminster Fuller, the molecule was named fullerene.

Ans. Detergents. These are sodium alkyl benzene sulphonates or sodium alkyl sulphates. Example: Sodium lauryl sulphate,

Detergents have replaced soap as a washing agent because unlike soap they can be used for washing purposes in cold water, acidic medium, hard water and have better cleansing action as compared to soap.

Ans. It is used as antifreeze because it has freezing point much below 0°C. If ethanol is not added to water, it will freeze in radiators. Mixture of water and alcohol does not corrode the material of the radiator.

Ans. (a) Add blue litmus paper into solution of acetic acid, it will turn red showing acidic nature.

(b) Add sodium bicarbonate. If there is brisk effervescence due to CO₂, it proves acidic nature.

Ans. (a) It is used as an antiseptic to sterlize wounds and syringes in hospitals. (b) It is used as an antifreeze in car radiators. (c) It is used as fuel in spirit lamps and internal combustion engines. (d) It is used in making alcoholic drinks e.g. whisky, wine, beer, etc.

Ans. When an ester reacts with water in presence of a base, a salt of carboxylic acid and an alcohol are produced. Such a reaction is called saponification. e.g. when ethyl ethanoate is boiled with a solution of sodium hydroxide, sodium ethanoate and ethanol are produced.

Ans. (a) Butane and ethene are produced.

(b) Ethanol is oxidised to form ethanoic acid.

Ans. When soap is added to hard water, calcium and magnesium salts present in it react with soap to form scum.

Ans. Advantages of synthetic detergents over soaps :

(a) Synthetic detergents can be used even with hard water also whereas soap cannot be used in hard water because soaps don’t produce lather readily with soap.

(b) Synthetic detergents are more soluble and have better cleansing action than soaps.

(c) Synthetic detergents can even be used with acidic water whereas soaps cannot be used.

Ans. Disadvantages of synthetic detergents over soaps

(a) Synthetic detergents are non-biodegradable and, therefore, can cause water pollution in lakes and rivers. This affects the fish and other aquatic organisms (because phosphatic salts present in detergents can cause rapid growth of algae in water bodies which further leads to decrease in the dissolved oxygen) resulting in the death of certain aquatic organisms.

(b) Synthetic detergents are also known to affect the texture and colour of the fabrics.

Ans. Ethanoic acid (CH₃COOH) is commonly known as acetic acid. The dilute solution of acetic acid in water (6-8%) is known as vinegar. The vinegar is used for preserving food, sausage, pickles, etc.

Ans. (a) It is used as a solvent.

(b) It is used to prepare alcoholic drinks.

Ans. Vinegar is prepared by the oxidation of ethanol in air, in the presence of acetobacter enzyme.

Ans. On treating with an alkali solution (sodium hydroxide) the ester is converted back to the constituent alcohol and sodium salt of the acid.

This reaction is hydrolysis of an ester. It takes place in presence of alkali and is known as saponification.

Soaps

Synthetic detergents

1. Soaps are sodium or potassium salts of higher fatty acids e.g sodium stearate. 2. Soaps are prepared from vegetable oils, animal and fats. 3. Soaps have relatively weak cleansing action. 4. Soaps form curdy white precipitate with calcium and magnesium salts present in hard water and hence, are not used in hard water. 5. Soaps cannot be used in acidic medium as they are decomposed into carboxylic acids in acidic medium. 6. Soaps do not cause water pollution.

1. Synthetic detergents are sodium alkyl sulphates or sodium alkyl benzene sulphonates e.g. sodium n-dodecylsulphate. 2. Synthetic detergents are prepared from the hydrocarbons obtained from petroleum. 3. They have strong cleansing action. 4. Calcium and magnesium salts of detergents are soluble in water and, therefore, no curdy white precipitates are obtained in hard water and hence synthetic detergents can be used even in hard water. 5. They can be used in acidic medium as they are the salts of strong acids and are not decomposed in acidic medium. 6. Synthetic detergents cause water pollution.

Ans. These are :

Ans. Carbon compounds are used in large number of industries such as those of food, fruits, paints, varnishes, sugar, paper, plastic etc.

Ans. Carbon has atomic number 6.

It has 4 electrons in its valence shell (2, 4).

Carbon can form a large number of compounds due to :

(a) Its tetracovalency

(b) Catenation.

Carbon forms both saturated and unsaturated compounds. It can form open chain as well as ring compounds.

1. All the organic compounds contain carbon. Carbon and its compounds are major sources of fuel.

2. The compounds of carbon are used in daily life, laboratories and industries.

Ans. A series of compounds having similar structural formulae, same functional group and hence similar chemical properties is called a homologous series.

For example, homologous series of aldehydes (or alkanals) can be represented as :

1. Any two adjacent members of a homologous series differ by CH₂ unit in their molecular formula.

2. Each homologous series has a general formula.

3. The members of a homologous series have the same functional group.

4. The members of a homologous series have similar chemical properties.

C₄H₁₀, C₂H₆, C₂H₄, CH₄, C₃H₈, C₃H₄.

Ans. C₂H₄ (C ≡ CH) and C₃H₄ (CH₃—C ≡ CH) will give addition reactions because they contain multiple bonds.

Ans. (i) Esterification. The reaction of carboxylic acid with an alcohol in the presence of concentrated sulphuric acid to form esters is called esterifications.

(ii) Decarboxylation. The reaction in which carbon dioxide is removed from a of carboxylic acid is known as decarboxylation. molecule

Ans. Denatured alcohol is 95% ethanol. To avoid misuse of ethanol for drinking purposes, it is made unfit by mixing it with some poisonous substances such as methanol, pyridine, copper sulphate etc. This process is called denaturing of alcohol and the alcohol thus formed is called denatured alcohol.

1. Litmus test

2. Sodium metal reaction

3. Sodium bicarbonate test.

Test	Ethanol	Ethanoic acid
1. Litmus test 2. Sodium metal test 3. Sodium bicarbonate test	No effect H₂ gas is evolved No reaction	Turns blue litmus red H₂ gas is evolved Brisk effervescence due to the evolution of CO₂.

Ans. Hard water contains Ca²⁺ and Mg²⁺ ions which react with soap molecules forming insoluble precipitates called scum. Due to this reason, soap is not able to form lather and cannot do the cleansing action. In this way, soap gets wasted when used with hard water.

1. It is used in the manufacture of dyes, perfumes and rayon.

2. It is used in the manufacture of plastics, rubber and silk industries.

3. It is used as a solvent.

4. It is used as a vinegar in cooking, as food dressing and for preparing pickles.

5. It is used for the manufacture of chemicals like acetone, acetic anhydride, etc.

Ans. Ammonia (NH₃), Glucose (C₆H₁₂O₆).

Ans. The compound is ethylene, C₂H₄ and its structural formula is

Ans. The covalent bond is generally formed between the atoms of non-metals and both the combining atoms are short of electrons than the stable nearest noble gas configurations in their outermost orbits.

Ans. CH₃CH₂CHO : Propanal

        CH₃COCH₃ : Propanone.

Ans. Ethanol containing five per cent methanol is known as rectified spirit.

Ans. CH₃CH₂OH + 3O₂ → 2CO₂ + 3H₂O

Ans. Acetic acid CH₃COOH.

Ans. A is methanoic acid, HCOOH. It turns blue litmus red.

HCOOH + NaHCO₃ → HCOONa + CO₂ +H₂O

Ans. X is ethyl alcohol (ethanol) i.e. C₂H₅OH

Ans. (a) Fourth member: C₄H₉OH

(b) Fifth member: C₅H₁₁OH

Ans. CH₃CH₂OH + 3O₂ → 2CO₂ + CH₂O

Ans. Common salt is added to precipitate out soap completely from oil or fat.

Ans. Ethanol.

Ans. This is due to the presence of free or mobile electrons.

(A) carboxylic acid

(B) aldehyde

(C) ketone

(D) alcohol.

Ans. (C) ketone

(A) 6 covalent bonds

(B) 7 covalent bonds

(C) 8 covalent bonds

(D) 9 covalent bonds.

Ans. (B) 7 covalent bonds

(A) 7 covalent bonds

(B) 8 covalent bonds

(C) 9 covalent bonds

(D) 10 covalent bonds.

Ans. (D) 10 covalent bonds.

(A) Oil droplets

(B) Dirt molecules

(C) Miscelles

(D) All.

Ans. (C) Miscelles

(A) Structural isomers

(B) Homologues

(C) Same compound

(D) None of these.

Ans. (A) Structural isomers

(A) CH₃ unit

(B) CH₂ unit

(C) CH unit

(D) C₂H₄ unit.

Ans. (A) CH₃ unit

(A) Combustion

(B) Substitution reaction

(C) Addition reaction

(D) Oxidation.

Ans. (C) Addition reaction

(A) Antibiotic

(B) Analgesic

(C) Antacid

(D) Antiseptic.

Ans. (C) Antacid

(A) Propanone

(B) Acetaldehyde

(C) Ethanoic acid

(D) Hydrochloric acid.

Ans. (C) Ethanoic acid

(A) – OH

(B) – COOH

(C) – CHO

(D) >C=O

Ans. (B) – COOH

(A) Propanone

(B) Acetaldehyde

(C) Ethanoic acid

(D) Hydrochloric acid.

Ans. (B) Acetaldehyde

(A) Insoluble in water

(B) Insoluble in oil

(C) Insoluble in greese

(D) None of these.

Ans. (A) Insoluble in water

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