deepak sir 9811291604 carbon classx/ · 2019-04-23 · deepak sir 9811291604 carbon classx/ 2 | p a...

Deepak sir 9811291604 classx/carbon

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What is combustion?

Combustion is a chemical process. It is defined as follows:

A chemical reaction in which heat and light (in the form of a flame) are given out is called combustion.

Combustion may also be defined as follows:

Combustion is a rapid oxidation/burning of any substance in which heat and light is produced.

Combustion of some common substances are described below:

Combustion of carbon. Carbon (or charcoal) burns in an or oxygen to give COz producing heat and light.

Combustion of hydrocarbons. Hydrocarbons burn to produce carbon dioxide (C02), water (H20) and heat and light. For

example, burning of methane is described by the following equation.

Natural gas and biogas contain methane. So, burning of natural gas and biogas are also combustion reactions.

Burning of LPG (which contains mainly butane) produces CO2 , H20, and heat and light.

Combustion of cellulose. Wood, paper, cotton cloth, all contain cellulose. Cellulose is a carbohydrate and can be described by

the formula (C6H10O5)n. On combustion, cellulose (like wood, cotton, cloth and paper) gives C02 and H20 as follows

Combustion of alcohol. Alcohols, such as, ethanol burn to give a flame and heat

Combustion is an exothermic process because heat is given out during combustion.

Naphthalene (moth balls), camphor etc. burn with a sooty flame.

Combustion and the nature of flame

Different carbon compounds burn with different characteristics.

Saturated hydrocarbons such as, methane, ethane, propane, butane and natural gas (which mainly contains methane) and LPG

(which mainly contains butane) burn with a blue flame in the presence of sufficient/excess of air/oxygen.

The presence of limited amount of air/oxygen, saturated hydrocarbons, such as, methane, butane, etc. give smoky flame.

Unsaturated compounds such as, ethane, ethyne etc., burn with a luminous/yellow smoky flame.

Kerosene when burnt in the presence of excess air gives smokeless blue flame. Kerosene when burnt in a pressure stove gives

blue flame.

In a wick-type stove, usually kerosene gives yellow smoky flame. Many-a-times, you might have seen the bottom of cooking

utensils getting blackened. This might be due to the blockage of the air holes in the stove.

Certain aromatic hydrocarbons such as, benzene, naphthalene etc., burn with a sooty flame, giving thick black clouds of

smoke.

Coal and petroleum on burning produce mainly carbon dioxide and small quantities of carbon monoxide, oxides of nitrogen

and sulphur.

The oxides of nitrogen and sulphur cause air pollution.

oxidation

Carbon and its compounds can be easily oxidised on combustion (or burning). During combustion /burning, the compound

gets oxidised completely to the product of highest oxidation level that is carbon dioxide. Oxidation of carbon and its

compounds under controlled conditions produce different products. For example,

Carbon gives carbon monoxide or carbon dioxide depending upon the oxygen available.

Hydrocarbons when oxidised give different products as follows:

For example, methane when oxidised give different products under different conditions.


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Alcohols also give different products on oxidation depending upon the reaction conditions. When heated with alkaline

KMn04 or acidified K2Cr207, alcohols give a carboxylic acid containing the same number of carbon atoms. For example, ethanol

when heated with alkaline KMn04 (or acidic K2Cr207) gives ethanoic acid.

ADDITION REACTIONS

What are the addition reactions

All unsaturated hydrocarbons (or in general all unsaturated carbon compounds) contain one or more double bonds or triple bonds.

These double or triple bonds have a tendency to get converted to single bond by the addition of small molecules, such as, hydrogen

(H2), halogens (X2), water (H20) and halogen acids (HX) across them. Such reactions are called addition reactions.

An addition reaction can be described by the following general chemical reaction :

Addition of hydrogen to unsaturated hydrocarbons gives saturated hydrocarbons.

Examples showing the addition of hydrogen to some unsaturated hydrocarbons are described below:

□ Addition of hydrogen to ethane

Ethane (C2H4) is an unsaturated hydrocarbon containing a double bond between the two carbon atoms. Due to the presence of C =

C double bond, ethane gives addition reaction with hydrogen. During the addition of hydrogen, ethene molecule adds up one

molecule of hydrogen across the double bond to give ethane (saturated hydrocarbon).

□ Addition of hydrogen to ethyne

Ethyne combines with hydrogen in the presence of nickel catalyst to give first ethene and finally ethane.

Addition of hydrogen to an unsaturated compound such as alkenes and alkynes is called hydrogenation.

Hydrogenation reaction

Addition of hydrogen to a unsaturated carbon compound is called hydrogenation reaction.In industry, hydrogenation reaction is

used for preparing vegetable ghee from vegetable oils. Vegetable oils such as groundnut oil, cotton seed oil, which contain double

bonds in their molecules, are converted to ghee by hydrogenation in the presence of Ni. The process of converting a vegetable oil

into a solid fat (vegetable ghee) is called hydrogenation of oil.

What are substitution reactions?

The reactions in which one or more hydrogen atoms of a molecule are replaced by some other atoms or groups are called

substitution reactions.

Saturated hydrocarbons (alkanes) give substitution reactions. For example, Methane reacts with chlorine (or bromine) in the

presence of sunlight or a halogen-carrier to give haloalkanes in which one or more H-atoms are replaced by equal number of

halogen atoms.


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The substitution reaction in which one or more hydrogen atoms are replaced by an equal number of halogen atoms is called

halogenation.

Examples to understand

Q.1. Which of the following hydrocarbons undergo addition reactions: C2H6, C3H8, C3H6, C2H2 and CH4?

Ans. Addition reactions are given by unsaturated hydrocarbons. In this list, of compounds, the compounds C3H6 and C2H2 are

unsaturated compounds. Therefore, the hydrocarbons C3H6 and C2H2 will give addition reaction.

Q.2. A mixture of oxygen and ethyne is burnt for welding. Why do you think a mixture of ethyne and air is not used?

Ans. Ethyne (C2H2) has higher percentage of carbon. Oxygen present in air is about 20% (the rest being mainly nitrogen). This

quantity of oxygen is not sufficient for the complete combustion of ethyne. For welding, higher temperature is needed.So, to ensure

complete combustion of ethyne, oxygen is used in welding torch.

Q.3. What will be the formula and electron dot structure of cyclopentane? (Self practice).

Q4. Give a test that can be used to differentiate chemically between butter and cooking oil.

Ans. Butter contains saturated fatty acids, whereas cooking oil contains unsaturated fatty acids. The unsaturation in a carbon

compound can be tested with bromine solution.

Take a few drops of oil in a test tube. In another test tube melt a little butter. Add a few drops of bromine water into both the test

tubes and shake. The colour of bromine gets decolourised by cooking oil but remain unaffected by butter.

Q.5. While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

(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. The correct answer is (b).

When the fuel does not burn completely, it produces smoke. Smoke contains carbon particles which blacken the outside surface of

the cooking utensil.

Answer the following:

1. Name the products of combustion of coal and wood.

2. What is the cause of blackening on the outside of the bottom of a cooking utensil?

3. Which solid fuels give flame? Give reason.

4. Write the chemical equation for the partial oxidation of methane.

5. Name the product formed when ethanol is oxidised using alkaline potassium permanganate.

6. Write a general chemical equation representing the addition reaction.

7. How does a substitution reaction differ from an addition reaction?

8. Name one industrial application of the addition reaction.

ETHANOL (ETHYL ALCOHOL, C2H5OH)

Ethanol (C2H5OH) is the second member of the homologous series of alcohols. The common name of ethanol (C2H5OH) is ethyl

alcohol is commonly known as alcohol. So, when the term alcohol is used, it means ethyl alcohol (or ethanol).

How is ethanol (ethyl alcohol) prepared?

Ethanol is prepared on commercial scale by fermentation of sugar. Molasses is a cheap source of sugar. It is a dark-coloured

viscous liquid left after the crystallisation of sugar from the concentrated sugarcane juice. Molasses contains about 30% of left-

over (which does not crystallise out) sugar.

Molasses is diluted to three times its volume by adding water. Then, the yeast extract is added to the dilute solution of molasses.

The yeast extract contains the enzymes called invertase and zymase. Fermentation is allowed to take place at 298 - 303 K in the

absence of air. This is because ethanol (ethyl alcohol) gets oxidised to ethanoic acid (acetic acid) in the presence of air. The

reactions, taking place during fermentation are

The slow decomposition of large organic molecules by enzymes is known as fermentation. For example, sugar molecules are

broken down into ethanol and carbon dioxide by the action of enzymes called invertase and zymase present in the yeast.

What are the physical properties of ethanol?

Ethanol is a typical and the most widely used alcohol. Some important physical properties of ethanol are given below.

From this dilute solution, ethanol is recovered by

fractional distillation. This gives about 93-95% pure

ethanol.

The fermented liquor so obtained contains up to 10% of

ethanol.


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□ Physical state, colour and odour. Ethanol is a colourless, inflammable liquid with a spirituous odour and burning taste.

□ Boiling and melting points. Ethanol boils at 78.1 °C, and freezes at - 118 °C.

□ Solubility. Ethanol is miscible (or soluble) with water in all proportions. Ethanol dissolves in water due to the formation of

hydrogen bonds with water molecules.

□ Conductivity. Ethanol does not conduct electricity. This is because ethanol is a covalent compound and it does not contain ions.

□ Action on litmus. Ethanol is a neutral compound. So, it has no effect on the colour of litmus.

What are the chemical properties of ethanol?

Ethanol gives all typical chemical reactions of alcohols. Some important chemical reactions given by ethanol are described below.

Combustion (or burning). Ethanol is an inflammable liquid. Ethanol burns in air with a pale-blue flame forming carbon

dioxide, water and evolving heat. Thus, combustion of ethanol is an exothermic reaction.

Reaction with sodium metal. Ethanol reacts with sodium metal to liberate hydrogen gas.

The reaction in which an alcohol reacts with a carboxylic acid in the presence of cone. H2S04 to form an ester is called

esterification.

Esters are sweet-smelling compounds and are used for making perfumes.

Oxidation.

Ethanol can be oxidised by any of the methods given below:

• With chromic anhydride. Chromicanhydride (Cr03) in acetic acid (CH3COOH) oxidises ethanol to ethanal.

By using alkaline potassium permanganate. Alkaline potassium permanganate (KMn04(alk)) oxidises ethanol to

ethanoic acid (acetic acid).

Reaction with ethanoic acid (Esterification reaction). Ethanol when heated with ethanoic acid (acetic acid) in the presence

of cone. H2S04 gives ethyl ethanoate (an ester). Ethyl ethanoate is a sweet-smelling compound.

In this reaction , Concentrated sulphuric acid acts as a dehydrating agent in the dehydration reaction.

□ Dehydration reaction. Ethanol when heated with excess of concentrated sulphuric acid at 443 K, gets dehydrated to give ethene.

What are the uses of ethanol Ethanol is used

As a fuel for lamps and stoves

As a substitute of petrol in internal combustion engines of scooters and cars

As a solvent for drugs, tinctures, oils, perfumes, inks, dyes, varnishes, etc.

As a beverage

As a preservative for biological specimens

As an antifreeze for automobile radiators

For the manufacture of terylene and polythene

As a raw material for large number of organic compounds such as esters, chloroform, iodoform, etc.

As an antiseptic to sterilize wounds and syringes in hospitals

What are the harmful effects of drinking alcohol?

Ethanol is commonly called alcohol. Ethyl alcohol is the only alcohol used in alcoholic beverages. Clinically, alcohol is intoxicant.

A person who drinks alcohol regularly becomes an addict to alcohol.Some of the harmful effects of drinking alcohol are:


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❖ Drinking of alcohol causes loss of senses and slows down his/her reflex actions. Larger intake of alcohol may lead to the loss of

consciousness.

❖ Drinking of alcohol over a long period of time damages liver.

What is denatured alcohol?

Ethanol (ethyl alcohol) to which certain poisonous and nauseating substances like methyl alcohol, pyridine, copper sulphate etc.,

have been added is termed denatured alcohol.

What are the harmful effects of drinking denatured alcohol Drinking denatured alcohol has the following harmful effects:

❖ Drinking denatured alcohol affects vision and may cause blindness.

❖ Drinking denatured alcohol causes unconsciousness or may even cause death.

A concentration of about 0.4% of ethyl alcohol in the blood of an individual may cause death.

Why is alcohol denatured?

❖ Ethanol is one of the most important industrial chemical. All alcoholic beverages contain ethanol (alcohol). The alcohol to be

used in industry is subjected to lower excise duty, whereas the alcoholic beverages are subjected to very high excise duty. Thus,

the alcohol to be used in industry is cheaper. To prevent its misuse for drinking purposes, the alcohol to be used in industry is made

unfit for drinking by adding certain poisonous substances. This is called denaturation of alcohol.

❖ To prevent the misuse of ethanol, industrial alcohol is coloured blue so that it can be recognised easily.

Few questions to understand

Q.1. Which gas is evolved during the process of fermentation?

Ans. During fermentation, carbon dioxide (C02) gas is evolved.

Q.2. An organic compound A of molecular formula C2H60 on oxidation gives an acid B with the same number of carbon atoms in

the molecule as A. Compound A is often used for sterilization of skin by doctors. Name the compounds A and B. Write the chemical

equation involved in the formation of B from A.

Ans. The given information can be summarized as follows:

The compound B is an organic acid containing two carbon atoms. B should contain one - COOH group. Therefore, acid B is

CH3COOH (acetic acid, ethanoic acid). A carboxylic acid can be obtained by the oxidation of an alcohol. Ethyl alcohol is

commonly used for the sterilization of skin. So, the compound A (C2H60) is an alcohol. Therefore, A is C2H5OH (ethyl alcohol,

ethanol).

Q.3. Why is a mixture of water and alcohol used instead of water in radiators of vehicles in cold

countries? Give two reasons.

Ans. Water is used in the radiators of automobiles to keep the engine cool. Water freezes at 0°C. Thus, in cold countries where the

temperature may fall much below 0°C, water cannot be used in radiators. Under these conditions, a mixture of water and alcohol is

used in radiators. Alcohol is used because,

(i) Alcohol and water mixture is homogeneous, i.e. alcohol and water are

Completely miscible in all proportions, (if) Alcohol and water mixture (generally 1 : 1 by volume) has much lower freezing point

than water. So, it does not freeze under low temperature Antifreeze coolant conditions.

Q.4. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?

Ans. Conversion of ethanol to ethanoic acid is an oxidation reaction because it involves,

(i) Addition of oxygen to the ethanol molecule, (if) Removal of hydrogen from the ethanol molecule.

Q.5. Butanone is a four-carbon compound with the functional group:

(a) carboxylic acid (b) aldehyde

(c) ketone (d) alcohol

Ans. The correct answer is (c).

Butanone is a ketone. It contains >C = O (called ketonic) group.

Q.6. Draw the structures for the following compounds:

(i) Ethanoic acid (ii) Bromopentane*

(Hi) Butanone (iv) Hexanal

*Are structural isomers possible for bromopentane?

Ans. Structures of the given compounds are shown below:

Yes. Structural isomers are possible for bromopentane .


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.

ETHANOIC ACID (or ACETIC ACID)

Ethanoic acid is well known for over centuries in the form of vinegar. Vinegar contains about 5-8% of ethanoic acid. In the

combined state as salt or ester, it is present in biological fluids and plant extracts. Ethanoic acid is commonly known as acetic

acid.

What are the physical properties of ethanoic acid (or acetic acid)

Some common physical properties of ethanoic acid (or acetic acid) are described below.

❖ At ordinary temperature, ethanoic acid is a colourless liquid with a strong pungent smell and sour taste.

❖ On cooling below 16.5 °C, it forms ice-like crystals. That is why, it is named as glacial acetic acid.

❖ It has a corrosive action on the skin and causes blisters.

❖ It is miscible with water due to the formation of hydrogen bonds with water molecules.

❖It dissolves sulphur, iodine and many other organic compounds.

What are the chemical properties of ethanoic acid?

Ethanoic acid, (CH3COOH) is a typical carboxylic acid. The main chemical reactions given by ethanoic acid are described below:

□ With water. In aqueous solutions, ethanoic acid ionises to produce H30+ and CH3COO- ion in accordance with the reaction,

The tendency of this reaction for the forward direction is very small. Thus, ethanoic acid is a weak acid.

□ Acidic nature. Ethanoic acid is a weak acid. It reacts with alkalis such as NaOH, decomposes sodium hydrogencarbonate

and sodium carbonate, giving salts and water.

o With metals. Ethanoic acid reacts with active metals, such as Na, Mg, Al and Zn to form the corresponding

metal ethanoates and hydrogen gas.

o With NaOH. Ethanoic acid reacts with strong alkalis such as NaOH giving sodium ethanoate and water.

o With sodium carbonate and sodium hydrogencarbonate. Ethanoic acid decomposes sodium hydrogencarbonate

and sodium carbonate with a rapid evolution of carbon dioxide gas.

Reactions of ethanoic acid with NaOH, NaHC03, Na2C03, and active metals (e.g., Na) show that the hydrogen present in

the carboxyl (- COOH) group is acidic in nature.

Ethanoic acid is much weaker than acids such as, hydrochloric acid, sulphuric acid etc.

Reaction with alcohols( Esterification reaction). Ethanoic acid reacts with alcohols in the presence of dehydrating agents,

e.g. cone. H2S04 to form an ester. For example, ethanoic acid when warmed with ethanol in the presence of cone. H2S04

gives ethyl ethanoate, (an ester).

The reaction of a carboxylic acid with an alcohol to form an ester is called esterification.

In esterification reaction, cone, sulphuric acid acts both as a catalyst as well as a dehydrating agent.

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

Esters can be hydrolysed in the presence of an acid to give back the parent carboxylic acid and the alcohol.

For example,

a. Ethyl ethonate on hydrolysis give ethnonoic acid and ethnol.


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Hydrolaysis of ester in presence of alkali is called saponification reaction

.

Alkaline hydrolysis of higher esters is used in the manufacture of soaps.

On alkaline hydrolysis, ethyl ethanoate gives ethanol and sodium salt of ethanoic acid.

What are the uses of ethanoic acid (acetic acid?)

❖ Ethanoic acid is used in the manufacture of various dyes, perfumes and rayon.

❖ Salts of ethanoic acid are used in paints and also in certain medicines.

❖ Ethanoates of aluminium and chromium are used as mordants.

❖ For making synthetic vinegar which is used in pickels, etc.

❖ Used as a solvent.

❖ Used for coagulating the latex.

❖ For making white lead (2PbC03.Pb(OH)2).

❖ Q.l. Write two tests to demonstrate that acetic acid (CH3COOH) is acidic in nature.

❖ (CBSE 1992 Comptt.)

❖ Ans. Following tests can be performed to show that acetic acid is acidic in nature.

❖ ( /) Litmus test. To a small quantity of acetic acid, add a few drops of blue litmus solution. Blue litmus turns red, indicating

acetic acid to be acidic in nature.

❖ (ii) Sodium bicarbonate test. To a small sample of acetic acid add a few drops of sodium bicarbonate solution. Brisk

effervescence due to the evolution of carbon dioxide confirms the acidic nature of acetic acid.

Ethanoic acid

1. Give IUPAC name of CH3COOH. (CBSE1998)

2. Write the molecular formula of ethanoic acid.

3. Fermentation of sugar solution with enzymes is being carried out in a vessel at 20-30°C in the presence of air. Which organic

compound will be produced in this process? (CBSE1996)

4. Complete the following statement:

Vinegar is prepared by the bacterial oxidation of ............................................................................................

5. Name the organic acid present in vinegar.

6. Why is ethanoic acid considered a weak acid?

Any substance which can remove grease and dirt from any fabric or body is called a detergent.

SOAPS AND DETERGENTS

Any substance which has the cleaning properties in water is called a detergent. Common soap is a typical detergent.

Now-a-days, however, the term detergent is applied to non-soapy synthetic detergents only. So, in common language, when we

talk of a detergent, we really mean a synthetic detergent.

What are soaps

Sodium or potassium salt of a long chain fatty acid (those containing 15-18 carbon atoms) is called a soap. A fatty acid is

described by the general formula RCOOH. So, soaps can be described by the formula RCOO-- Na+ or RCOO--K+. Thus, a soap

molecule consists of an anion RCOO" and a cation Na+ or K+.

Soaps are prepared by alkaline hydrolysis of oils or fats (triglycerides). Alkaline hydrolysis of oils or fats is called

saponification.

What are synthetic detergents?

Sodium salts of sulphonic esters are called synthetic detergents. Some typical synthetic detergents are

♦Linear alkylbenzene sulphonate

where R is a long chain alkyl group. The most common detergent in this class is sodium n-dodecylbenzene sulphonate.

❖ Sodium lauryl sulphate, C12H32OSO3--Na +

❖ The molecule of a synthetic detergent has two ends, viz., hydrophobic (water-repellent) end of the hydrocarbon chain, and

hydrophilic (water-attracting) end, usually an acidic or a basic group.


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For sodium n-dodecylbenzene sulphonate, the two ends are shown .

How does soap clean or remove dirt from a dirty cloth?

A molecule of soap is made up of the following two parts:

❖ A polar part consisting of COONa+. This is called polar end.

♦ A nonpolar part consisting of a long chain of 12 to 18 carbon atoms. This is called hydrocarbon end.

The polar end of a soap - COO"Na+ is water-soluble, whereas the hydrocarbon part is water-repellent and oil-soluble. The two

parts of a soap molecule are shown

When an oily (dirty) piece of a cloth is put into soap solution, the hydrocarbon part of the soap molecule attaches itself to the oily

drop, and the - COO- end orients itself towards water. The Na+ ions in solution arrange themselves around the - COO" ions. The

negatively charged micelle so formed entraps the oily dirt as shown

The negatively charged micelles repel each other due to the electrostatic repulsion. As a result, the tiny oily dirt particles do not

come together and get soap washed away in water during rinsing.

What are the limitations of a soap

Soaps have the following limitations.

□ Soaps do not act efficiently in hard water. In hard water, due to the presence of Ca2+ and Mg2+ ions, soaps give insoluble

calcium and magnesium salts of fatty acids. These precipitates, called scum, stick to the fabric and make their cleaning difficult.

Thus, in hard water, a soap does not give lather.

Soaps are not effective in acidic solutions. In acidic solutions, a soap gets decomposed to give free fatty acid, which remains

sticking to the clothes.

How do soaps differ from detergents

Although both soaps and detergents possess cleansing property, but the two differ from each other in several ways. The main

differences between a soap and a detergent are given below.

What advantages do synthetic detergents have over soaps?

Both synthetic detergents and soaps are used for cleansing. But synthetic detergents have some advantages over soaps. As a result,

synthetic detergents are considered better than soaps.


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Some advantages that synthetic detergents have over soaps are listed below.

❖ Synthetic detergents are prepared from hydrocarbons obtained from petroleum, whereas soaps are prepared from oils which are

becoming scarce. Thus, synthetic detergents help us to save oils.

❖ Synthetic detergents can be used for washing even in hard water. Soaps cannot be used for washing in hard water. In hard water,

soaps form curdy precipitate which sticks to the fabric.

❖ Synthetic detergents have stronger cleansing power than soaps.

❖ Synthetic detergents can be used even in the acidic solution, whereas soaps cannot be used in acidic solutions. This is because

soaps decompose under acidic conditions to give free fatty acids.

Q1. Explain the formation of scum when hard water is treated with soap.

Ans. When soap solution is added into a sample of hard water, scum is formed. This is due to the formation of calcium or

magnesium salts of the fatty acids.

(A) Very short answer type questions

Why does carbon form covalent bonds?

What is meant by single, double and triple covalent bonds? Give one example of each.

Give three characteristics of covalent compounds.

Describe the structure of graphite.

Discuss the term catenation. Why does carbon show strong catenation tendency?

What are the functional groups? What is meant by a functional group in an organic compound? Give the structural formula of the functional groups in

(a) acetic acid, and (b) ethyl alcohol.)

Name the functional groups in aldehydes and ketenes. Draw the structural formula of this functional group.

Describe the rules for naming the straight chain hydrocarbons.

Illustrate by giving an example, the method of naming carboxylic acids.

Write the first five members of the alkenes homologous series.

How will you identify a hydrocarbon from its name?

What are addition reactions? Give an example.

A neutral organic compound is warmed with ethanoic acid and little cone. H2S04.Vapour having sweet smell (fruity smell) is evolved. What type of functional group is present in this organic compound?

Write the chemical equations for the reaction of ethanoic acid (acetic acid) with (a) ethanol in presence of cone. H2S04 (b) Na metal (c) NaHCQ3 (sodium bicarbonate)

Property Soap Synthetic detergent

1. Chemical nature Soap is the sodium or potassium salt of higher fatty acid. The ionic group in soaps is - COO~Na+

Synthetic detergents are the sodium salts of a long chain alkylbenzene sulphonic acid or long chain alkylhydrogensulphates. The ionic group in synthetic detergents is - S03" Na+ or - S04"Na+

2. Preparation Soaps are prepared from animal fat or

vegetable oils.

Synthetic detergents are prepared from hydrocarbons obtained from petroleum.

3. Biodegradability Soaps are biodegradable. Common synthetic detergents are not biodegradable.

4. Suitability in hard water Soaps are not suitable for washing in hard water.

Synthetic detergents can be used for washing even in hard water.

5. Cleansing action Soaps have weak (mild) cleansing action. Synthetic detergents have strong cleansing

action.


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An organic compound A has the molecular formula C2H60. On oxidation in air in the presence of heated copper as catalyst, it is oxidised to CH3COOH. What is the compound A? Give equation for the reaction?

(B) Short answer type questions

1. Show the formation of ammonia molecule. 2. What is meant by a polar covalent bond? Give one example. 3. What is meant by saturated and unsaturated carbon compounds? Give one example of each type. 4.How is the branched chain hydrocarbons named? 5.Write the general formulae of alkanes, alkenes and alkynes. 6.What is a substitution reaction? Give one example. 7.How do alcohols differ structurally from alkanes? Describe the basic steps involved in the preparation of ethanol from sugar 8.An organic compound 'X' is a constituent of wine and beer. This compound on oxidation forms another organic compound 'Y' which is a constituent of vinegar. 9.Identify the compounds 'X' and 'Y'. Write the chemical equation of the reaction that takes place to form the compound 'Y'.

10An organic compound having molecular formula C2H4O2 gives brisk effervescence with sodium bicarbonate. Give name and the structural formula of the compound. 11. What happens when (i) a carboxylic acid is heated with an alcohol in the presence of cone. H2S04?

(ii) a few drops of saturated solution of sodium bicarbonate are added to a small quantity of ethanoic acid?

(C) Long answer type questions

1. What is fermentation? How is ethanol prepared by fermentation? Give any two uses of ethanol. (CBSE 1992 Comptt., 1994)

2. An organic compound 'X' which is sometimes used as antifreeze has the molecular formula C2H60. 'X' on oxidation gives a compound 'Y' which gives effervescence with baking soda solution. What can 'X' and 'Y' be? Write their

structural formulae. (CBSE 1997)

3. What are saturated and unsaturated hydrocarbons? How will you identify a hydrocarbon from its formula? 4. What is meant by combustion? Write the chemical reaction describing the combustion of wood. 5. What is meant by hydrogenation reaction? Mention one of its industrial application. 6. How do soaps differ from synthetic detergents?

7. Describe the mechanism of the cleansing effect of soaps.

(D) Multiple choice type questions (Tick (✓) the correct answer)

1. The organic compounds containing - OH group are called (a) acids (b) aldehydes □ (c) alcohols (d) esters □ 2. Alcohols are (a) neutral (b) acidic □ (c) Basic (d) amphoteric □

3. Which class of organic compounds gives effervescence with NaHC03 solution? (a) esters □ (b) alcohols □ (c) carboxylic acids □ (d) aldehydes □ 4. Carboxylic acids are obtained from alcohols by (a) Oxidation □ (b) reduction □ (c) hydrolysis □ (d) pyrolysis □

5. The number of electron pairs shared by the two atoms which are bonded by a double bond is (a) 1 □ (b)2 □ (c) 3 □ (d) 4 □

6. The property of carbon atom by virtue of which it forms bonds with other carbon atoms is called (a) Chemical bonding □ (b) catenation □ (c) Carbonisation □ (d) polymerization □ 7. Soaps are prepared by alkaline hydrolysis of (a) Carboxylic acids □ (b) lower esters □ (c) Higher esters □ (d) none of these □


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ANSWERS TO MULTIPLE CHOICE QUESTIONS

1. C 2. (a) 3. (c) 4. (a) 5. (B) 6. (b) 7. (c)

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