Chapter 11 -Carbon and its Compounds. Chemistry.

12 Dec 2020 10:53 am

Chapter 11, Carbon and its Compounds.   Chemistry, sslc, chemistry, science, sslc, tamilnadu board, full solution,

I. Choose the best answer:

Question 1.

The molecular formula of an open-chain organic compound is C3H6. The class of the compound is:

(a) alkane

(b) alkene

(c) alkyne

(d) alcohol

Answer:

(b) alkene

Question 2.

The IUPAC name of an organic compound is 3-Methyl butan-1-ol. What type of compound it is?

(a) Aldehyde

(b) Carboxylic acid

(c) Ketone

(d) Alcohol

Answer:

(d) Alcohol

Question 3.

The secondary suffix used in IUPAC nomenclature of an aldehyde is:

(a) – ol

(b) – oic acid

(c) – al

(d) – one

Answer:

(c) – al

Question 4.

Which of the following pairs can be the successive members of a homologous series?

(a) C3H8 and C4H10

(b) C2H2 and C2H4

(c) CH4 and C3H6

(d) C2H5OH and C4H8OH.

Answer:

(a) C3H8 and C4H10

Hint: Two successive members of a homologous series must have a difference of -CH2 in the molecular formula.

C3

.

Question 5.

C2H5OH + 3O2 → 2CO2 + 3H2O is a:

(a) Reduction of ethanol

(b) Combustion of ethanol

(c) Oxidation of ethanoic acid

(d) Oxidation of ethanal

Answer:

(b) Combustion of ethanol

Question 6.

Rectified spirit is an aqueous solution which contains about ______ of ethanol.

(a) 95.5 %

(b) 75.5 %

(c) 55.5 %

(d) 45.5 %.

Answer:

(a) 95.5 %

Rectified spirit is a mixture of 95.5 % of ethanol and 4.5 % of water.

Question 7.

Which of the following are used as anaesthetics?

(a) Carboxylic acids

(b) Ethers

(c) Esters

(d) Aldehydes

Answer:

(b) Ethers

Question 8.

TFM in soaps represents _____ content in soap.

(a) mineral

(b) vitamin

(c) fatty acid

(d) carbohydrate.

Answer:

(c) fatty acid

Hint: TFM – Total Fatty Matter. It corresponds the fatty acid (oil).

Question 9.

Which of the following statements is wrong about detergents?

(a) It is a sodium salt of long chain fatty acids

(b) It is sodium salts of sulphonic acids

(c) The ionic part in a detergent is – SO3 –Na+

(d) It is effective even in hard water.

Answer:

(a) It is a sodium salt of long-chain fatty acids

II. Fill in the blanks:

1. An atom or a group of atoms which is responsible for chemical characteristics of an organic compound is called …………

2. The general molecular formula of alkynes is ………..

3. In IUPAC name, the carbon skeleton of a compound is represented by ………. (root word / prefix / suffix)

4. (Saturated / Unsaturated) ……….. compounds decolourize bromine water.

5. Dehydration of ethanol by cone. Sulphuric acid forms ………. (ethene/ ethane)

6. 100 % pure ethanol is called ………..

7. Ethanoic acid turns ………… litmus to …………

8. The alkaline hydrolysis of fatty acids is termed as …………

9. Biodegradable detergents are made of …………. (branched / straight) chain hydrocarbons.

Answer:

1. Functional group

2- CnH2n-2

3. root word

4. unsaturated

5. ethene

6. absolute alcohol

7. Blue, red

8. Saponification

9. straight

III Match the following:

Question 1.

Match the Column I and Column II.

Answer:

A. (iii)

B. (iv)

C. (v)

D. (ii)

E. (i)

IV. Assertion and Reason:

Answer the following questions using the data given below:

Question 1.

Assertion: Detergents are more effective cleansing agents than soaps in hard water.

Reason: Calcium and magnesium salts of detergents are water soluble.

(a) Assertion and Reason are correct, Reason explains the Assertion.

(b) Assertion is correct, Reason is wrong.

(c) Assertion is wrong, Reason is correct.

(d) Assertion and Reason are correct, Reason doesn’t explains Assertion.

Answer:

(a) Assertion and Reason are correct, Reason explains the Assertion.

Question 2.

Assertion: Alkanes are saturated hydrocrabons.

Reason: Hydrocarbons consits of covalnet bonds.

(a) Assertion and Reason are correct, Reason explains the Assertion .

(b) Assertion is correct, Reason is wrong.

(c) Assertion is wrong, Reason is correct.

(d) Assertion and Reason are correct, Reason doesn’t explains Assertion.

Answer:

(d) Assertion and Reason are correct, Reason doesn’t explains Assertion.

V. Short answer questions:

Question 1.

Name the simplest ketone and give its structural formula.

Answer:

The simplest ketone is Propanone.

It’s structural formula:

Question 2.

Classify the following compounds based on the pattern of carbon chain and give their structural formula:

(i) Propane

(ii) Benzene

(iii) Cyclo butane

(iv) Furan.

Answer:

Question 3.

How is ethanoic acid prepared from ethanol? Give the chemical equation.

Answer:

Ethanol is oxidized to ethanoic acid with alkaline KMnO4 or acidified K2Cr2O7.

Question 4.

How do detergents cause water pollution? Suggest remedial measures to prevent this pollution?

Answer:

Some detergents having a branched hydrocarbon chain are not fully biodegradable by microorganisms present in water. So, they cause water pollution.

They have straight hydrocarbon chains, in biodegradable detergents, which can be easily degraded by bacteria.

Question 5.

Differentiate soaps and detergents.

Answer:

VI. Long answer questions.

Question 1.

What is called a homologous series? Give any three of its characteristics?

Answer:

A homologous series is a group or a class of organic compounds having the same general formula and similar chemical properties in which the successive members differ by a – CH2 group.

Characteristics of homologous series:

All members of a homologous series contain the same elements and functional group.

All members of a homologous series can be prepared by a common method.

Chemical properties of the members of a homologous series are similar.

Question 2.

Arrive at, systematically, the IUPAC name of the compound: CH3-CH2– CH2-OH.

Answer:

Step 1: The parent chain consists of 3 carbon atoms. The root word is ‘Prop’.

Step 2: There are single bonds between the carbon atoms of the chain. So, the primary suffix is ‘ane’.

Step 3: Since, the compound contains – OH group, it is an alcohol. The carbon chain is numbered from the end which is closest to – OH group. (Rule 3)

Step 4: The locant number of – OH group is l and thus the secondary suffix is ‘l-ol’.

The name of the compound is Prop + ane + (l – ol) = Propan-l-ol

Question 3.

How is ethanol manufactured from sugarcane?

Answer:

Ethanol is manufactured in industries by the fermentation of molasses, which is a by-product obtained during the manufacture of sugar from sugarcane. Molasses is a dark coloured syrupy liquid left after the crystallization of sugar from the concentrated sugarcane juice. Molasses contain about 30% of sucrose, which cannot be separated by crystallization. It is converted into ethanol by the following steps:

(i) Dilution of molasses : Molasses is first diluted with water to bring down the concentration of sugar to about 8 to 10 percent.

(ii) Addition of Nitrogen source : Molasses usually contains enough nitrogenous matter to act as food for yeast during the fermentation process. If the nitrogen content of the molasses is poor, it may be fortified by the addition of ammonium sulphate or ammonium phosphate.

(iii) Addition of YeastrThe solution obtained in step (ii) is collected in large ‘fermentation tanks’ and yeast is added to it. The mixture is kept at about 303K for a few days. During this period, the enzymes invertase and zymase present in yeast, bring about the conversion of sucrose into ethanol.

The fermented liquid is technically called wash.

(iv) Distillation of ‘Wash’: The fermented liquid (i.e., wash), containing 15 to 18 percent alcohol, is now subjected to fractional distillation. The main fraction drawn is an aqueous solution of ethanol which contains 95.5% of ethanol and 4.5% of water. This is called rectified spirit. This mixture is then refluxed over quicklime for about 5 to 6 hours and then allowed to stand for 12 hours. On distillation of this mixture, pure alcohol (100%) is obtained. This is called absolute alcohol.

ASTER CLASSES 10th Science Guide Chapter 11 Carbon and its Compounds

Question 4.

Give the balanced chemical equation of the following reactions:

(i) Neutralization of NaOH with ethanoic acid.

Answer:

(ii) Evolution of carbon dioxide by the action of ethanoic acid with NaHCO3.

Answer:

(iii) Oxidation of ethanol by acidified potassium dichromate.

Answer:

(iv) Combustion of ethanol.

Answer:

Question 5.

Explain the mechanism of cleansing action of soap.

Answer:

A soap molecule contains two chemically distinct parts that interact differently with water. It has one polar end, which is a short head with a carboxylate group (-COONa) and one non – polar end having the long tail made of the hydrocarbon chain.

The polar end is hydrophilic (Water-loving) in nature and this end is attracted towards the water. The non – polar end is hydrophobic (Water hating) in nature and it is attracted towards dirt or oil on the cloth, but not attracted towards the water. Thus, the hydrophobic part of the soap molecule traps the dirt and the hydrophilic part makes the entire molecule soluble in water.

When soap or detergent is dissolved in water, the molecules join together as clusters called ‘micelles’. Their long hydrocarbon chains attach themselves to the oil and dirt. The dirt is thus surrounded by the non-polar end of the soap molecules. The charged carboxylate end of the soap molecules makes the micelles soluble in water. Thus, the dirt is washed away with the soap.

VII. Hot Questions.

Question 1.

The molecular formula of an alcohol is C4H10O. The locant number of its -OH group is 2.

(i) Draw its structural formula.

Answer:

(ii) Give its IUPAC name.

Answer:

Butan-2-ol

(iii) Is it saturated or unsaturated?

Answer:

Saturated

Question 2.

An organic compound ‘A’ is widely used as a preservative and has the molecular formula C2H4O2. This compound reacts with ethanol to form a sweet smelling compound ‘B’.

(i) Identify the compound ‘A’.

Answer:

Organic Compound ‘A’ with the molecules formula C2 H4 O2 which is a preservative is acetic acid (or) ethanoic acid.

A – CH3COOH

(ii) Write the chemical equation for its reaction with ethanol to form compound ‘B’.

Answer:

B – Ethyl ethanoate (ester – sweet smelling)

(iii) Name the process.

Answer:

Esterification

ASTER CLASSES 

Important Questions and Answers

I. Choose the best answer.

Question 1.

The general formula of alkane series is:

(a) CnH2n

(b) CnH2n-1

(C) CnH2n+2

(d) CnH2n-2

Answer:

(C) CnH2n+2


Question 2.

Organic compounds are _____ in nature.

(a) flammable

(b) inflammable

(c) heavy

(d) light.

Answer:

(b) inflammable


Question 3.

The Heterocyclic compound is:

(a) Benzene

(b) Pyridine

(c) Naphthalene

(d) Camphor

Answer:

(b) Pyridine


Question 4.

Pick out the unsaturated compound from the following ______.

(a) CH3 – CH2 – CH3

(b) CH3 – CH = CH2

(c) CH3

(d) both (b) and (c).

Answer:

(d) both (b) and (c).


Question 5.

……….. will decolourise Br2/H2O.

(a) Methane

(b) Pent-2-ene

(c) Ethyl alcohol

(d) Ethanal

Answer:

(b) Pent-2-ene


Question 6.

The simplest alkane is ______.

(a) Ethane

(b) Ethyne

(c) Propane

(d) Methane.

Answer:

(d) Methane.


Question 7.

……….. is the prefix used for -NH2 Group.

(a) Fluoro

(b) Methyl

(c) Amino

(d) Nitro

Answer:

(c) Amino


Question 8.

The IUPAC name of an organic compound is Pentan-2-one. The secondary suffix is:

(a) Pentan

(b) an

(c) -one

(d) -2-

Answer:

(c) -one


Question 9.

Molasses is fortified with ………… to increase the nitrogen content.

(a) (NH4)2SO4 (or) (NH4)3PO4

(b) (NH4)2CO3 (or) NH4Cl

(c) (NH4)2CO3 (or) NH4OH

(d) None of the above

Answer:

(a) (NH4)2SO4 (or) (NH4)3PO4


Question 10.

Which one of the following is a general formula for alkyne?

(a) CnH2n

(b) CnH2n+2

(c) CnH2n-2

(d) CnHn

Answer:

(c) CnH2n-2


II. Fill in the blanks.

1. The common difference between the successive member of the homologous series if ……….. group.

2. Denatured spirit is a mixture of ethanol and …………

3. Methane gas is produced when the sodium salt of ethanoic acid is ………… with soda lime.

4. For coagulating rubber from latex ………… is used.

5. ………… is added to prevent the caking of the detergent powder.

6. When a soap or detergent is added to water the moleculer cluster together to form ……….

7. The terminal functional group among aldehydes and ketones is ………..

8. On dehydrogenation of ethanol with Cu/573 K it gives ………… gas.

9. ……… converts glucose into ethanol and carbondi-oxide.

10. The structural formula of Pentanoic acid is …………

Answer:

1. -CH2

2. pyridine

3. decarboxylated

4. ethanoic acid

5. Na2SO4 or Sodium sulphate

6. micelles

7. aldehyde

8. H2

9. Zymase

10. CH3CH2CH2CH2COOH


III Match the following:

Question 1.

Match the column I and column II.

Answer:

A. (ii)

B. (iii)

C. (v)

D. (i)

E. (iv)

Question 2.

Match the column I and column II.

Answer:

A. (v)

B. (iv)

C. (i)

D. (iii)

E. (ii)

IV Assertion and Reason.

Answer the following questions using the data given below:

Question 1.

Assertion: Alkynes decolourise bromine water.

Reason: Alkynes are unsaturated compounds.

(a) Assertion and Reason are correct, Reason explains Assertion.

(b) Assertion is correct, Reason is wrong.

(c) Assertion is wrong, Reason is correct.

(d) Assertion and Reason are correct, Reason doesn’t explains Assertion.

Answer:

(a) Assertion and Reason are correct, Reason explains Assertion.

Question 2.

Assertion: Denaturation of ethanol makes it unfit for drinking purpose.

Reason: Ethanol is mixed with Pyridine for denaturation.

(a) Assertion and Reason are correct, Reason explains Assertion.

(b) Assertion is correct, Reason is wrong.

(c) Assertion is wrong, Reason is correct.

(d) Assertion and Reason are correct, Reason doesn’t explains Assertion.

Answer:

(a) Assertion and Reason are correct, Reason explains Assertion.

Question 3.

Assertion: Organic compounds contains covalent bond.

Reason: Organic compounds have low melting and boiling points.

(a) Assertion and Reason are correct, Reason explains Assertion.

(b) Assertion is correct, Reason is wrong.

(c) Assertion is wrong, Reason is correct.

(d) Assertion and Reason are correct, Reason doesn’t explains Assertion.

Answer:

(d) Assertion and Reason are correct, Reason doesn’t explains Assertion.

Question 4.

Assertion: Due to catenation a large number of carbon compounds are formed.

Reason: Carbon compounds show the property of allotropy.

(a) Assertion and Reason are correct, Reason explains Assertion.

(b) Assertion is correct, Reason is wrong.

(c) Assertion is wrong, Reason is correct.

(d) Assertion and Reason are correct, Reason doesn’t explains Assertion.

Answer:

(b) Assertion is correct, Reason is wrong.


V. Short answer questions:

Question 1.

Define isomerism with an example.

Answer:

Isomerism is a phenomenon in which organic compounds having the same molecular formula will have different structural formula.

Eg: for the molecular formula C2H6O we can write

CH3CH2OH – ethanol

CH4O CH3 – Methoxy methane

Question 2.

What are root words?

Answer:

Root words are the basic unit which describes the carbon skeleton. It gives the number of carbon atoms present in the parent chain of the compound and the pattern of their arrangement.

Question 3.

Write The functional group and the secondary suffix of the following compounds.

Answer:

Question 4.

What happens when ethanol is dehydrated with con.H2SO4 at 443K?

Answer:

Dehydration (Loss of water): When ethanol is heated with cone. H2SO4 at 443K, it loses a water molecule i.e., dehydrated to form ethene.

Question 5.

Write a note on esterification.

Answer:

The reaction of an alcohol with a carboxylic acid gives a compound having fruity odour. This compound is called an ester and the reaction is called esterification. Ethanol reacts with ethanoic acid in the presence of cone. H2SO4 to form ethyl ethanoate, an ester.

Question 6.

Write tests to identify the presence of ethanoic acid.

Answer:

Ethanoic acid turns blue litmus paper to red.

Ethanoic acid gives brisk effervescence when treated with Na2CO3

Ethanoic acid gives a sweet-smelling compound called ester when treated with ethanol.

Question 7.

Write a note on decarboxylation reaction.

Answer:

Decarboxylation (Removal of CO2): When a sodium salt of ethanoic acid is heated with soda lime (solid mixure of 3 parts of NaOH and 1 part of CaO), methane gas is formed.

Question 8.

What is hard soap?

Answer:

Soaps, which are prepared by the saponification of oils or fats with caustic soda (sodium hydroxide), are known as hard soaps. They are usually used for washing purposes.

Question 9.

Why ordinary soap is not suitable for using with hard water?

Answer:

Ordinary soaps when treated with hard water, precipitate as salts of calcium and magnesium. They appear at the surface of the cloth as sticky grey scum. Thus, the soaps cannot be used conveniently in hard water.

Question 10.

What are the advantages of detergents over soaps?

Answer:

Detergents are better than soaps because of they:

can be used in both hard and soft water and can clean more effectively in hard water than soap.

can also be used in saline and acidic water.

do not leave any soap scum on the tub or clothes.

dissolve freely even in cool water and rinse freely in hard water.

can be used for washing woollen garments, whereas soap cannot be used.

have a linear hydrocarbon chain, which is biodegradable.

are active emulsifiers of motor grease.

do an effective and safe cleaning, keeping even synthetic fabrics brighter and whiter.


VI. Long answer questions.

Question 1.

Write the IUPAC name of the following compounds

Answer:


Question 2.

Write the characteristics of organic compounds.

Answer:

Organic compounds have a high molecular weight and a complex structure.

They are mostly insoluble in water but soluble in organic solvents such as ether, carbon tetrachloride, toluene, etc.

They are highly inflammable in nature.

Organic compounds are less reactive compared to inorganic compounds. Hence, the reactions involving organic compounds proceed at slower rates.

Mostly organic compounds form covalent bonds in nature.

They have a lower melting point and boiling point when compared to inorganic compounds

They exhibit the phenomenon of isomerism, in which a single molecular formula represents several organic compounds that differ in their physical and chemical properties

They are volatile in nature.

Organic compounds can be prepared in the laboratory.

Question 3.

List the advantages of detergents over soaps.

Answer:

Can be used in both hard and soft water and can clean more effectively in hard water than soap.

Can also be used in saline and acidic water.

Do not leave any soap scum on the tub or clothes.

Dissolve freely even in cool water and rinse freely in hard water.

Can be used for washing woollen garments, where as soap cannot be used.

Have a linear hydrocarbon chain, which is biodegradable.

Are active emulsifiers of motor grease.

Do an effective and safe cleansing, keeping even synthetic fabrics brighter and whiter.

Question 4.

Draw the schematic diagram for the classification of organic compounds based on the pattern of carbon chain with example.

Answer:


Question 5.

Explain the manufacture of soap.

Answer:

Manufacture of soap by Kettle Process This is the oldest method. But, it is still widely used in the small scale preparation of soap. There are mainly, two steps to be followed in this process.

1. Saponification of oil: The oil, which is used in this process, is taken in an iron tank (kettle). The alkaline solution (10%) is added into the kettle, a little in excess. The mixture is boiled by passing steam through it. The oil gets hydrolysed after several hours of boiling. This process is called Saponification.

2. Salting out of soap: Common salt is then added to the boiling mixture. Soap is finally precipitated in the tank. After several hours the soap rises to the top of the liquid as a ‘curdy mass’. The neat soap is taken off from the top. It is then allowed to cool down.

Question 6.

Ethanol is heated with excess con.H2SO4 at 443K.

(a) Name the reaction that occurs and explain it.

Answer:

Dehydration (Loss of water).

When ethanol is heated with conc.H2SO4 at 443K, it loses a water molecule i.e., dehydrated to form ethene.

ASTER CLASSES 10th Science Guide Chapter 11 Carbon and its Compounds 

(c) What is the product formed? What happen when this gas is passed through Br2/H2O.

Answer:

Ethene gas.

When it is passed through Br2/H2O it gets decolourised because it is an unsaturated compound.

(d) Why does no decolourization occurs when ethanol is treated with Br2/H2O?

Answer:

Ethanol is a saturated compound. Therefore no decolourisation occurs.


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