Carbon and its compound class 10 chemistry NCERT MCQ & SAQ

 

Carbon and its compound class 10chemistry NCERT

Carbon and its compound class 1o chemistry NCERT SOLUTION:

1. What would be the electron dot structure of carbon dioxide which has the formula CO2?

 

 

 

2. What would be the electron dot structure of a molecule of sulfur which is made up of eight atoms of sulfur? (Hint - the eight atoms of sulfur are joined together in the form of a ring.)

 

Answer

 

 

 

 

1. How many structural isomers can you draw for pentane?

 

Three structural isomers are possible for pentane.

 

2. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?

The two features of carbon that give rise to a large number of compounds are as follows:

→ Catenation - It is the ability to form bonds with other atoms of carbon.

→ Tetravalency - With the valency of four, carbon is capable of bonding with four other atoms.

 

3. What will be the formula and electron dot structure of cyclopentane?

 

Answer

 

The formula for cyclopentane is C5H10. Its electron dot structure is given below.

 

 

 

 

 

 

 

 

Page No: 69

 

4. Draw the structures for the following compounds.

(i) Ethanoic acid (ii) Bromopentane*

(iii) Butanone (iv) Hexanal

*Are structural isomers possible for bromopentane?

 

 

 

(ii) There are many structural isomers possible for bromopentane. Among them, the structures of three isomers are given.

 

5. How would you name the following compounds?

 

Answer

 

(i) Bromoethane

(ii) Methanal (formaldehyde)

(iii) Hexyne

 

Page No: 71

 

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

 

Answer

 

CH3CH2OH + (Alkaline KMnO4) → CH3COOH

Since, in this reaction one oxygen is added to ethanol, hence it is an oxidation reaction.

 

2. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?

 

 

 

2HC ≡ CH + 5O2 → 4CO2 + 2H2O + Heat

When ethyne is burnt in air, it gives a sooty flame. This is due to incomplete combustion caused by limited supply of air. However, if ethyne is burnt with oxygen, it gives a clean flame with temperature 3000°C because of complete combustion. This oxy-acetylene flame is used for welding. It is not possible to attain such a high temperature without mixing oxygen. This is the reason why a mixture of ethyne and air is not used.

 

Page No: 74

 

1. How would you distinguish experimentally between an alcohol and a carboxylic acid?

 

Answer

 

We can distinguish between an alcohol and a carboxylic acid on the basis of their reaction with carbonates and hydrogen carbonates. Acid reacts with carbonate and hydrogen carbonate to evolve CO2 gas that turns lime water milky.

Alcohols, on the other hand, do not react with carbonates and hydrogen carbonates.

 

2. What are oxidizing agents?

 

Answer

 

Oxidizing agents are the substances that gain electrons in redox reaction and whose oxidation number is reduced.

 

Page No: 76

 

1. Would you be able to check if water is hard by using a detergent?

 

Answer

 

Detergent gives lather with hard and soft water both, while a soap gives lather with soft water only. Thus, it is not possible to check if water is hard; by using a detergent.

 

2. People use a variety of methods to wash clothes. Usually after adding the soap, they 'beat' the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?

 

Answer

 

A soap molecule has two parts namely hydrophobic and hydrophilic. With the help of these, it attaches to the grease or dirt particle and forms a cluster called micelle. These micelles remain suspended as a colloid. To remove these micelles, it is necessary to agitate clothes.

 

Page No: 77

 

Exercise

 

1. Ethane, with the molecular formula C2H6 has

(a) 6 covalent bonds.

(b) 7 covalent bonds.

(c) 8 covalent bonds.

(d) 9 covalent bonds.

► (b) 7 covalent bonds.

 

2. Butanone is a four-carbon compound with the functional group

(a) carboxylic acid.

(b) aldehyde.

(c) ketone.

(d) alcohol.

► (c) ketone.

 

3. 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.

► (b) the fuel is not burning completely.

 

4. Explain the nature of the covalent bond using the bond formation in CH3Cl.

 

Answer

 

The structure of CH3Cl is given below:

 

Carbon has four valence electrons. It shares 1 electron each with 3 hydrogen atoms and 1 electron with chlorine. The bond between C and Cl atoms is covalent but due to the higher value of electro-negativity of Cl, the C–Cl bond is polar in nature.

 

5. Draw the electron dot structures for

(a) ethanoic acid.

(b) H2S.

(c) propanone.

(d) F2.

 

Answer

 

 

 

6. What is a homologous series? Explain with an example.

 

Answer

 

A homologous series is a series of carbon compounds that have different numbers of carbon atoms but contain the same functional group.

 

For example, methane, ethane, propane, butane, etc. are all part of the alkane homologous series. The general formula of this series is CnH2n+2.

Methane CH4

Ethane CH3CH3

Propane CH3CH2CH3

Butane CH3­CH2CH2CH3

It can be noticed that there is a difference of -CH2 units between each successive compound.

 

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

 

Answer

 

Ethanol and Ethanoic acid be differentiated on the basis of their following properties:

→ Ethanol is a liquid at room temperature with a pleasant smell. Ethanoic acid has a melting point of 17°C. Since it is below room temperature, it freezes during winter. Moreover, ethanoic acid has a smell like vinegar.

→ Ethanol does not react with metal carbonates while ethanoic acid reacts with metal carbonates to form salt, water and carbon dioxide. For example,

2CH3COOH + Na2CO3 → 2CH3COONa + CO2 + H2O

→ Ethanol does not react with NaOH while ethanoic acid reacts with NaOH to form sodium ethanoate and water. For example,

CH3COOH + NaOH → CH3COONa + H2O→ Ethanol is oxidized to give ethanoic acid in presence of acidified KMnO4 while, no reaction takes place with ethanoic acid in presence of acidified KMnO4.

 

8. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?

 

Answer

 

Soap molecules have two ends. One end is hydrophilic and another end is hydrophobic. When soap is dissolved in water and clothes are put in the soapy solution, soap molecules converge in a typical fashion to make a structure; called micelle. The hydrophobic ends of different molecules surround a particle of grease and make the micelle; which is a spherical structure. In this, the hydrophilic end is outside the sphere and hydrophobic end is towards the center of the sphere. This is why micelle formation takes place when soap is added to water.

Since ethanol is not as polar as soap, micelles will not be formed in other solvents such as ethanol.

 

9. Why are carbon and its compounds used as fuels for most applications?

 

Answer

 

Carbon and its compounds give a large amount of heat on combustion due to the high percentage of carbon and hydrogen. Carbon compounds used as fuel have optimum ignition temperature with high calorific values and are easy to handle. Their combustion can be controlled. Therefore, carbon and its compounds are used as fuels.

 

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

 

Answer

 

Hard water often contains salts of calcium and magnesium. Soap molecules react with the salts of calcium and magnesium and form a precipitate. This precipitate begins floating as an off-white layer over water. This layer is called scum. Soaps lose their cleansing property in hard water because of formation of scum.

 

11. What change will you observe if you test soap with litmus paper (red and blue)?

 

Answer

 

Since soap is basic in nature, it will turn red litmus blue. However, the color of blue litmus will remain blue.

 

12. What is hydrogenation? What is its industrial application?

 

Answer

 

Hydrogenation is the chemical reaction between hydrogen and other compounds in the presence of a catalyst. Hydrogenation is used mainly to reduce saturated hydrocarbons. Hydrogenation is an additional reaction.For Example: When ethene is heated with the catalyst nickel it is reduced to ethane.

Industrial application:

→ >Hydrogenation is used in many industrial applications. For example; in the Petrochemical Industry, hydrogenation is used to convert alkenes into alkanes (paraffins) and cycloalkanes.

→ It is also used to prepare vegetable ghee from vegetable oils.

 

13. Which of the following hydrocarbons undergo addition reactions:

C2, H6, C3H8, C3H6, C2H2 and CH4.

 

Answer

 

Unsaturated hydrocarbons undergo additional reactions. Being unsaturated hydrocarbons, C3H6 and C2H2 undergo additional reactions.

 

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

 

Answer

 

Butter contains saturated fats. Therefore, it cannot be hydrogenated. On the other hand, oil has unsaturated fats. That is why it can be hydrogenated to saturated fats (solids).

 

15. Explain the mechanism of the cleaning action of soaps.

The dirt present on clothes is organic in nature and insoluble in water. Therefore, it cannot be removed by only washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the center of the cluster. These micelles remain suspended in the water. Hence, the dust particles are easily rinsed away by water.

 

Carbon and its compound class 1o chemistry NCERT MCQ

Question : A functional group mainly determines the

a) Physical properties

b) Chemical properties

c) Both

d) None of these

Answer : B

 

Question : 100% pure ethanol is called

a) Rectified spirit

b) Absolute alcohol

c) Denatured alcohol

d) Power alcohol

Answer : B

 

Question : Carboxylic acid containing one carbon atom is

a) Formic acid

b) Acetic acid

c) Citric acid

d) Vinegar

Answer : A

 

Question : The odor of acetic acid resembles that of:

a) Tomato

b) Kerosene

c) Vinegar

d) Lemon juice

Answer : C

 

Question : Sodium carbonate solution is added to dilute ethanoic acid) It is observed that :

a) A gas evolves

b) A solid settles at the bottom

c) The mixture becomes warm

d) The color of the mixture

Answer : A

 

Question : 2ml of acetic acid is added to 5ml of water and was shaken up for 1minute, it was noticed that:

a) The acid formed a separate layer on the top of water

b) Water formed a separate layer on the top of the acid

c) A clear and homogeneous solution is formed

d) A pink and clear solution is formed

Answer : C

 

Question : On adding NaHCO3 to acetic acid, a gas is evolved which turns lime water milky due to the formation of:

a) Calcium Carbonate

b) Calcium Hydroxide

c) Calcium bicarbonate

d) Calcium Acetate

Answer : A

 

Question : Which among the following contains triple bond:

a) C2H4

b) C2H2

c) C3H4

d) C2H6

Answer : B

 

Question : The number of covalent bonds in C5H12 is:

a) 15 b) 16 c) 17 d) 18

Answer : B

 

Question : Which amongst the following does not conduct electricity:

a) CH3COOH

b) C3H7OH

c) HCOOH

d) NaCl(aq)

Answer : B

 

 

Question : Methane reacts with one mole of Chlorine in the presence of sunlight to give _________.

The reaction is called_______.

a) Chloromethane, substitution

b) Dichloromethane, addition

c) Trichloromethane, elimination

d) Tetra chloro methane, combustion

Answer : A

 

 

Question : Catenation is maximum in:

a) Carbon

b) Oxygen

c) Sulfur

d) Phosphorous

Answer : A

 

 

Question : Ethane and ethene can be distinguished by using:

a) Bromine water

b) Chlorine water

c) I2

d) HCl

Answer : A

 

 

Question : The number of isomers of C6H14 are

a) 4 b) 5 c) 6 d) 7

Answer : C

 

 

Question : Which of the following represents cyclohexane:

a) C6H14

b) C6H12

c) C6H10

d) C6H6

Answer : B

 

 

Question : The IUPAC name of the following;

 

a) Butanal

b) Butanoic acid

c) Butanol

d) Pentane

Answer : C

 

 

Question : Which of the following are members of the same homologous series:

a) CH4 and C2H4

b) CH3OH and CH3Cl

c) C2H5OH and C3H7OH

d) CH3OCH3 and C2H5OH

Answer : C

 

 

Question : The difference in the molecular formula and molecular mass of CH4 and C2H6 is:

a) CH3 and 12u

b) CH2 and 12u

c) CH3 and 14u

d) CH2 and 14u

Answer : D

 

 

Question : Which of the following statements about diamond and graphite is true?

a) They have same crystal structure

b) They have same degree of hardness

c) They have same electrical conductivity

d) They have the same chemical properties.

Answer : D  

 

 

Question : Graphite is good conductor of electricity due to the

a) presence of hexagonal rings 

b) presence of ions

c) presence van der waal forces 

d) presence of free electron

 

Question : Which of the following is a crystalline form of carbon ?

a) Charcoal 

b) Coal 

c) Graphite 

d) Lamp black

 

Question : Which of the following statements regarding graphite is not correct?

a) Graphite is a black and soft crystalline substance

b) Graphite is manufactured by heating coke at 3000oC.

c) Graphite is a bad conductor of heat and electricity.

d) Graphite possesses a metallic luster and soapy touch.

 

Question : Organic compounds will always contains

a) carbon 

b) hydrogen

c) nitrogen 

d) sulfur

 

Question : Organic compounds are generally

a) covalent in nature 

b) ionic in nature

c) insoluble in organic solvents 

d) soluble in water

 

Question : The isomers always possess similar

a) chemical properties 

b) molecular formula

c) physical properties 

d) structural formula

 

Question : No of protons, electrons and neutrons respectively in carbon atom is

a) 6,6,8 

b) 6,6,6 

c) 8,6,8 

d) 6,7,8

 

Question : A compound with the molecular formula C2H2 must contain

a) all single bonds 

b) one double bond

c) one triple bond 

d) none of the above

 

Question : The general formula of alkane series is

a) Cnh2n–2 

b) Cn H2n 

c) Cnh2n+2 

d) Cn H2n+4

 

Question : The next higher homologue of propane is

a) C2H6 

b) C3H4 

c) C4H10 

d) C5H12 

 

 

Question : The correct IUPAC name of the compound

 

a) 4-methylpent-1-ene 

b) 2-methylpent-4-ene 

c) 4-methylhex-1-ene 

d) 3-methylhex-1-ene

 

Question : IUPAC name of the compound given below is

a) 2-methyl-3-ethyl-1-pentene 

b) 3-ethyl-4-methyl-4-pentene

c) 3-ethyl-2-methyl-1-pentene 

d) 3-methyl-2-ethyl-1-pentene

 

Question : Which of the following names is wrong for CH2=CHCH2Cl ?

a) Chloro propene 

b) 1-Chloroprop-3-ene

c) 3-Chloroprop-1-ene 

d) 3-Chloropropylene

 

 

Question : Which of the following represents neopentyl alcohol ?

a) CH3CH(CH3)CH2CH2OH 

b) (CH3)3CCH2OH

c) CH3CH2CH2CH2OH 

d) CH3CH2CH(OH)CH2

 

Question : The IUPAC name of acetyl acetone is :

a) 2,5–pentanedione 

b) 2,4–pentanedione

c) 2,4–hexanedione 

d) 2,4–pentanedione

 

Question : IUPAC name of the compound is :

a) 4, 4-di(formylmethyl) butanal 

b) 2-(formylmethyl) butane-1, 4-dicarbaldehyde

c) hexane-3-acetaldol 

d) 3-(formylmethyl) hexanedial

 

Question : The IUPAC name of is :-

a) 1-Hydroxy-4-methylpentanoic acid 

b) 1-Methyl-3-hydroxypentanoic acid

c) 4-Hydroxy-2-methylpentanoic acid 

d) 4-Carboxypentanol-2

 

Question : The correct IUPAC name of the compound is :

a) 4-Bromo-1-chloro-2-fluoro iodo methyl butene

b) 4-Bromo-2-chloromethyl-1-fluoro-1-iodobut-1-ene

c) 2-(2-Bromoethyl)-3-chloro-1-fluoro-1-iodoprop-1-ene

d) 1-Bromo-3-chloromethyl-4-fluoro-4-iodobut-1-ene

 

Question : The IUPAC name of

a) propanal 

b) propanol

c) propionic aldehyde 

d) 2-methylbutanal

 

Question : Which of the following pairs is an example of chain isomer ?

a) CH3 – CH2 – OH and CH3OCH3

b) CH3 – CH2 – CHO and CH3 – COCH3

c) CH3 – CH2 – CH2 – CH2 – CH3 and CH3–(CH3)CH–CH2–CH3

d) All of the above

 

Question : The oxidation of CH3CH2CHO produces

a) CH3COOH 

b) CH3CH2COOH

c) CH3COCH3  

 

Question : Identify the 'product' in the reaction CH3COOH + C2H5OH → conc.H2SO4  Product + H2O

a) alcohol 

b) aldehyde 

c) ketone 

d) ester

 

Question : Identify the 'product' in the reaction CH3COOH → LiAIH4 'product' + H2O

a) aldehyde 

b) alcohol 

c) ketone 

d) acid

 

Question : The 'product' in the reaction CH3CH2OH 350ºC → Al2O3 'product' + H2O is

a) alkane 

b) alkene 

c) alkyne 

d) none of these

 

Question : The 'product' of the reaction CH2 = CH2 [O]→KMnO4 'product' is

a) CH3COOH 

b) HOCH2CH2OH

c) COOH

     ↓

     COOH

d) none of these

 

Question : Total number of non-cyclic structural isomers of C4H10 are

a) 5 

b) 7 

c) 2 

d) 4

 

Question : Oils on treating with hydrogen in the presence of palladium or nickel catalyst form fats. This is an example of

a) Addition 

b) Displacement

c) Substitution 

d) Oxidation

 

Question : Oxidation of alcohol in presence of alk.KMnO4 results in formation of

a) aldehyde

b) ester 

c) acid 

d) ketone

 

Question : C2H5OH in presence of conc) H2SO4 convert into ethene. What role does sulphuric acid play here ?

a) reducing agent 

b) oxidizing agent

c) dehydrating agent 

d) both B and C

 

Question :  Which of the following statements about diamond and graphite is true?

• a) They have the same chemical properties.

• b) They have same crystal structure

• c) They have same degree of hardness

• d) They have same electrical conductivity

Answer :  They have the same chemical properties.

 

Question :  The difference in the molecular formula and molecular mass of CH4 and C2H6 is:

• a) CH2 and 14u

• b) CH3 and 12u

• c) CH2 and 12u

• d) CH3 and 14u

Answer :  CH2 and 14u

 

Question :  Which of the following are members of the same homologous series:

• a) C2H5OH and C3H7OH

• b) CH4 and C2H4

• c) CH3OH and CH3Cl

• d) CH3OCH3 and C2H5OH

Answer :  C2H5OH and C3H7OH

 

Question :  The IUPAC name of the following;

• a) Butanol

• b) Butanal

• c) Butanoic acid

• d) Pentane

Answer :  Butanol

 

Question :  Which of the following represents cyclohexane:

• a) C6H12

• b) C6H14

• c) C6H10

• d) C6H6

Answer :  C6H12

 

Question :  The number of isomers of C6H14 are

• a) 6

• b) 4

• c) 5

• d) 7

Answer :  6

 

Question :  Ethane and ethene can be distinguished by using:

• a) Bromine water

• b) Chlorine water

• c) I2

• d) HCl

Answer :  Bromine water

 

Question :  Catenation is maximum in:

• a) Carbon

• b) Oxygen

• c) Sulfur

• d) Phosphorous

Answer :  Carbon

 

Question :  Methane reacts with one mole of Chlorine in the presence of sunlight to give _________. The reaction is called_______.

• a) Chloromethane, substitution

• b) Dichloromethane, addition

• c) Trichloromethane, elimination

• d) Tetra chloro methane, combustion

Answer :  Chloromethane, substitution

 

Question :  Which amongst the following does not conduct electricity:

• a) C3H7OH

• b) CH3COOH

• c) HCOOH

• d) NaCl(aq)

Answer :  C3H7OH

 

Question :  The number of covalent bonds in C5H12 is:

• a) 16

• b) 15

• c) 17

• d) 18

Answer :  16

 

Question :  Which among the following contains triple bond:

• a) C2H2

• b) C2H4

• c) C3H4

• d) C2H6

Answer :  C2H2

 

Question :  On adding NaHCO3 to acetic acid, a gas is evolved which turns lime water milky due to the formation of:

• a) Calcium Carbonate

• b) Calcium Hydroxide

• c) Calcium bicarbonate

• d) Calcium Acetate

Answer :  Calcium Carbonate

 

Question :  2ml of acetic acid is added to 5ml of water and was shaken up for 1minute, it was noticed that:

• a) A clear and homogeneous solution is formed

• b) The acid formed a separate layer on the top of water

• c) Water formed a separate layer on the top of the acid

• d) A pink and clear solution is formed

Answer :  A clear and homogeneous solution is formed

 

Question :  Sodium carbonate solution is added to dilute ethanoic acid It is observed that :

• a) A gas evolves

• b) A solid settles at the bottom

• c) The mixture becomes warm

• d) The color of the mixture

Answer :  A gas evolves

 

Question :  The odor of acetic acid resembles that of:

• a) Vinegar

• b) Tomato

• c) Kerosene

• d) Lemon juice

Answer :  Vinegar

 

Question :  Carboxylic acid containing one carbon atom is

• a) Formic acid

• b) Citric acid

• c) Acetic acid

• d) Vinegar

Answer :  Formic acid

 

Question :  100% pure ethanol is called

• a) Absolute alcohol

• b) Acetic acid

• c) Denatured alcohol

• d) Power alcohol

Answer :  Absolute alcohol

 

Question :  A functional group mainly determines the

• a) Chemical properties

• b) Physical properties

• c) Both

• d) None of these

Answer :  Chemical properties

 

Question :  — C=O represents the functional group:

• a) ketones

• b) Alcohols

• c) Carboxylic acids

• d) Acids

Answer :  ketones

Carbon and its compound class 1o chemistry NCERT SAQ

 Give a chemical test to distinguish between saturated and unsaturated  hydrocarbons.

(b) (i) Name the products formed when ethanol burns in air. ‘

(ii) What two forms of energy are liberated from burning alcohol?

(c) Why is the reaction between methane and chlorine considered a substitution

reaction?

Answer.

 Name the carbon compound which on heating with excess of concentrated sulphuric acid at 443 K gives ethene.

Answer.

Name the compound formed when ethanol is warmed with ethanoic acid in the

presence of a few drops of cone.H2S04

Answer.

What is meant by a functional group in an organic compound? Name the functional group present in

(i) CH3CH2OH

(ii) CH3COOH

(b) State one point of difference between soap and synthetic detergent.

Answer.

(a) Functional group is an atom or group of atoms or reactive part of compound, which determines chemical properties of compounds.

(i) —OH (Alcohol)

(ii) —COOH (Carboxylic acid)

(b) Soaps do not work well with hard water, detergents work well with hard water.

 Give reasons for the following observations:

(a) The element carbon forms a very large number of compounds.

(b) Air holes of a gas burner have to be adjusted when the heated vessels get blackened by the flame.

(c) Use of synthetic detergents causes pollution of water.

Answer.

(a) Carbon forms a large number of compounds since carbon is small in size and can form stable covalent bonds (catenation) and it shows tetravalency.

(b) Air holes of gas burners are made open (adjusted) so that air can pass through, which is needed for complete combustion, so that heated vessels do not get blackened.

(c) Some synthetic detergents are non-biodegradable, therefore, cause pollution of water.

 What is ethanoic acid? Write the formula of the functional group present in this acid.

What special name is given to its 5 – 8% solution in water? How does ethanoic acid react with sodium carbonate? Write a chemical equation of the reaction and common name of the salt produced.

Answer.

 State two characteristic features of carbon which when put together give rise to large

number of carbon compounds.

Answer. (i) Catenation (ii) Tetravalency of carbon

Question.15 Write the structural formula of chloroethane.

Answer.

 Name the functional group of organic compounds that can be hydrogenated. With the help of suitable examples explain the process of hydrogenation mentioning the conditions of the reaction and any one change in physical property with the formation of the product. Name any one natural source of organic compounds that are hydrogenated.

Answer.

When unsaturated hydrocarbons are heated with hydrogen in the presence of nickel as a catalyst, saturated hydrocarbons are formed. If the starting unsaturated hydrocarbons are liquids, they will change into solids. Vegetable oils are hydrogenated to form vegetable ghee. Plants are natural sources of vegetable oils which can be hydrogenated.

 An ester has the molecular formula C4H8O2. Write its structural formula. What happens when this ester is heated in the presence of sodium hydroxide solution? Write the balanced chemical equation for the reaction and name the products. What is a saponification reaction?

Answer.

Out of HCL and CH3COOH, which one is a weak acid and why? Describe an activity to

support your answer.

Answer. Acetic acid ( CH3COOH) is a weaker acid because it does not dissociate completely into its ions in aqueous solution.

Activity: Add zinc metal in HCI and CH3COOH respectively. The hydrogen gas will be evolved faster in HCI and slowly in CH3COOH. It shows acetic acid is a weak acid.

Alternative Method:

If we use pH paper, the color of pH paper will be dark red in HCI and light red in CH3COOH which shows HCI is a strong acid and CH3COOH is a weak acid.

Q 1. An organic compound 'A' has the molecular formula C2H4O2 and is acidic in nature, on heating with alcohol and conc. Sulphuric acid, vapors with pleasant or fruity smell are given out. What is this chemical compound 'A,' and what is the chemical equation involved in the reaction?    (CBSE All India 1999)

• The compound 'A' with molecular formula C2H4O2 is ethanoic acid (acetic acid). 

• Upon heating with ethanol (ethyl alcohol) and concentrated sulphuric acid, ethyl ethanoate (ethyl acetate) is formed as the product. 

• It is an ester with a pleasant or fruity smell. 

• The reaction is known as the esterification reaction.

• 

 

Q 2. An organic compound 'A' is a constituent of antifreeze and has the molecular formula C2H6O. Upon reaction with alkaline KMnO4, the compound 'A' is oxidized to another compound 'B' with the formula C2H6O2. Identify the compounds 'A' and 'B'. Write the chemical equation for the reaction, which leads to the formation of 'B'.    (CBSE All India 2000 Comptt.)

• The compound 'A' is ethanol, and with alkaline KMnO4, it is oxidized to ethanoic acid 'B'. 

• The chemical equation for the reaction is:
  

 

Q 3. Name the functional groups present in the following compounds:

(i) CH3—CH2—CH2 —OH 

(ii) CH3—CH2—CH2 —COOH

(iii) CH3—CH2—CHO 

(iv) CH3—CO—CH2—CH 3

(i) —OH (alcohol)

(ii) —COOH (carboxylic acid) 

(iii) —CHO (aldehyde) 

(iv) —CO— (ketone)

 

Q 4. Write the formulae of the compounds and name the functional groups present in each of them

(i) Ethanoic acid

(ii) Propanone

(iii) Nitromethane  (C.B.S.E. Delhi 2005) 

(i) Ethanoic acid: CH3COOH (carboxylic acid)

(ii) Propanone: CH3COCH3 (ketone)

(iii) Nitromethane: CH3NO2 (nitro)

 

Q 5. Name the enzyme which converts:

(i) milk into curd (yogurt)

(ii) cane sugar into glucose and fructose

(iii) glucose into ethanol.  (C.B.S.E. Foreign 2005) 

(i) Lactase converts milk into curd.

Milk to Curd

(ii) Invertase converts cane sugar (sucrose) into glucose and fructose.

(iii) Zymase converts glucose into ethanol.

 

Q 6. (i) Name the gas evolved during the fermentation process.    

(C.B.S.E. Delhi 2006)

(ii) List the two products formed when enzyme invertase acts on sugar present in molasses.

(i) CO2 gas is evolved, accompanied by brisk effervescence.

(ii) Glucose and fructose are the products when enzyme invertase acts on sucrose (C12H22O11) present in molasses.

 

Q 7. Complete the following equations and write the names of the products formed. (C.B.S.E. Delhi 2007)

(i) CH3COOH + NaOH

(ii) C2H5OH + O2

(iii) CH3COOH + C2H5OH

 

Q 8. Name the organic compound present in vinegar.

(C.B.S.E. All India 2007)

The organic compound present in vinegar is ethanoic acid, also called acetic acid. 

 

Q 9. (a) Why does carbon form compounds by covalent bonding?

(b) An organic acid 'X' is a liquid that often freezes during wintertime in cold countries. It has the molecular formula C2H4O2. On warming with ethanol in the presence of a few drops of sulphuric acid, a compound `Y' with a sweet smell is formed.

(i) Identify X and 'Y'. 

(ii) Write the chemical equation for the reaction involved.    (C.B.S.E. Delhi 2008)

(a) Carbon forms covalent compounds because it is tetravalent, i.e., it has 4 valence electrons and therefore shares its electron and forms covalent bonds.

(b) 

• The available information suggests that the organic acid X with molecular formula C2H4O2 is ethanoic acid (CH3COOH). 

• It reacts with ethanol in the presence of a few drops of sulphuric acid on warming to give ethyl ethanoate ester with a pleasant smell.
  

 

Q 10. Why do covalent compounds have low melting and boiling points?    (C.B.S.E. All India 2008)

• In covalent compounds, the atoms are linked by covalent bonds formed by electron sharing.

• Since no ions are present in these, the attractive forces are quite weak.

• As a result, the covalent compounds have low melting and boiling points.

 

 

 

 

 

 

 

 

 

 

 

Q 11. (a) How are carboxylic acids different from mineral acids from an ionisation point of view?

(b) Describe an activity to find how ethanoic acid reacts with sodium carbonate. Name the gas evolved. How can it be tested?

(a) 

• Carboxylic acids (organic acids) are less ionized in solution as compared to mineral acids (HCI, HNO3, H2SO4, etc.) 

• Due to this reason, these are weaker acids than mineral acids.

(b) 

• Take a small volume of ethanoic acid in a tube. Add a few drops of sodium carbonate (Na2CO3) solution prepared in water to the tube. 

• A colorless gas(CO2) with brisk effervescence will evolve. When the gas is passed through lime water, it will become milky.
  Na2CO3(aq) + CH3COOH(aq) → CH3COONa(aq) + H2O(l) + CO2(g)
  Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)
  Lime water (Milky)

 

Q 12. (a) What is a functional group in a carbon compound? Identify the functional group present in CH3COOH and C2H5OH.

(b) State the principle on which the cleansing action of soap is based. (C.B.S.E. Foreign 2008) 

(a) 

• A functional group may be defined as an atom or group of atoms upon which the properties of a particular organic compound are based.

• Different families differ in functional groups.
  Functional group in CH3COOH : (—COOH) carboxylic acid
  Functional group in C2H5OH : (—OH) alcohol

(b) 

• The cleansing action of soap is based on its tendency to act as a bridge between water and oil drops containing dirt particles. 

• As a result, oil and water get mixed. 

• They form a stable emulsion, also called micelle. 

• This helps in removing oil drops containing dirt particles from clothes. The clothes become clean.

 

Q 13. (a) Draw the structure of the following compounds.

(i) Ethanoic acid

(ii) Butanone

(b) Why is the conversion of ethanol to ethanoic acid considered an oxidation reaction? (C.B.S.E. Forigen 2008)

(a) 

(b) When ethanol (C2H5OH) changes with ethanoic acid (CH3COOH)

• There is a decrease in the number of hydrogen atoms by two.

• There is an increase in the number of oxygen atoms by one. 

• Therefore, the conversion represents an oxidation reaction.

 

 

 

 

 

 

 

 

Q 14. (a) What are esters? How are they formed? 

(b) Write two uses of esters?

(a) 

• Esters are the group of organic compounds which contain the function group (COOR) called ester group.

• The value of R may change as —CH3, —C2H5, —C3H7, etc.
  Example:
  (Methyl Ethanoate) 

• Esters are formed as a result of a chemical reaction called esterification reaction.

(b) Uses of Esters

• Esters have a pleasant smell. These are used as flavoring agents and also in perfumes.

• Esters of glycerol known as triglycerides are used in the manufacture of soaps. This reaction is called the saponification reaction.
  

 

Q 15. Distinguish between esterification and saponification reactions of organic compounds.    (C.B.S.E. All India 2008)

(a) In the esterification reaction, an acid reacts with alcohol in the pressure of conc. H2SO4 to form an ester with a pleasant or fruity smell.

Example:

(b) Saponification is quite different from esterification because, in this case, an ester reacts with an alkali (NaOH or KOH) to form a salt of acid and alcohol.

Example:

 

Q 16. (a) In organic compounds, which part largely determines the physical and chemical properties.

(b) Write a chemical equation to represent the reaction of ethanol with an acidified solution of potassium dichromate.

(a) 

• In organic compounds, it is the functional group which largely determines the physical and chemical properties of compounds.

• Actually, an organic compound is made up of two parts. These are the alkyl group and the functional group.

• These are responsible for the characteristics of the compounds.
  Example:
  The properties of alkanols (OH is the functional group) are different from those of alkanoic acid (COOH is the functional group). For more details, consult the text part.

(b) 

• An acidified solution of potassium dichromate (K2Cr2O7) forms chromic acid (H2CrO4).

• It releases oxygen to bring about the oxidation of ethanol (CH3CH2OH), first to ethanal and then to ethanoic acid(CH3COOH).
  

 

Q 17. Give reasons for the following:

(a) Air holes of the gas burners have to be adjusted when heated vessels get blackened by the flame.

(b) Use of synthetic detergents causes pollution problems.

(a)

• In case the vessel where cooking is done gets blackened from outside, this means that combustion is incomplete.

• As a result, the carbon particles in the form of soot get deposited, and the vessel becomes black from outside.

• In order to check this, oxygen or air supply must be increased. This can be done only by adjusting the air holes of the gas burner.

(b) 

• The pollution problems caused by synthetic detergents are due to their non-biodegradable nature.

• These are actually long-chain organic compounds which do not break or decompose in water.

• Naturally, this will result in pollution problems.

• Some of the detergents are even of toxic nature and will make water unfit for drinking.

Carbon and its compound class 1o chemistry NCERT LONG QUESTION

 (a) In tabular form, differentiate between ethanol and ethanoic acid under the following heads:

(i) Physical state (ii) Taste

(iii) NaHCO3 test (iV) Ester test

(b) Write a chemical reaction to show the dehydration of ethanol.

Answer. 

State two properties of carbon which lead to a very large number of carbon compounds.

(b) Why does micelle formation take place when soap is added to water? Why are micelles not formed when soap is added to ethanol?

Answer.

(a) (i)-Catenation (ii) Tetravalency

(b) It is because a large number of molecular ions of soaps get aggregated and form colloidal solutions. Soap has a hydrophobic tail (hydrocarbon) which dissolves in the hydrocarbon part and the hydrophilic part dissolves in water. Ethanol is non-polar solvent therefore micelles are not formed because the hydrocarbon part gets attracted towards ethanol and the ionic end will not dissolve in alcohol.

 Explain isomerism. State any four characteristics of isomers. Draw the structures of possible isomers of butane, C4H10

Answer. Isomerism is a phenomenon due to which some compounds have the same molecular formula but different structural formulae.

Characteristics:

(i) They differ in structural formula.

(ii) They differ in melting point.

(iii) They differ in boiling point.

(iv) They differ in solubility in the same solvent.

 What are isomers? Draw the structures of two isomers of butane, C4H10. Why can’t we have isomers of the first three members of the alkane series?

Answer. Those compounds, which have the same molecular formula but different structural formulae are called isomers.

In the first three members of the alkane series, branching is not possible. Therefore, we cannot have isomers.

 Define homologous series of organic compounds. List its two characteristics. Write the name and formula of the first member of the series of alkenes.

Answer. The series of organic compounds having the same functional group and similar chemical properties is called the homologous series.

Each member differs from successive members by —CH2— group. The difference in molecular weight between two successive members is 14 u.

Characteristics:

(i) It has the same general formula, from which all members can be derived.

(ii) They have similar chemical properties.

C2H4, CH2=CH2, Ethene is the first member of the alkene series.

Complete the following equations:

Answer.

 What is the difference between the chemical composition of soaps and detergents? State in brief the action of soaps in removing an oily spot from a shirt. Why are soaps not considered suitable for washing where water is hard?

Answer. oaps are sodium or potassium salts of fatty acids having — COONa group. Detergents are

sodium or potassium salts of sulfonic acids having — SO3Na and — SO4Na group. Cleansing action of soap: Soap molecules consist of a large hydrocarbon tail which is hydrophobic (water-hating or water repelling) with a negatively charged head which is hydrophilic (water-loving) as shown in figure.

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

 List in tabular form three physical and two chemical properties on the basis of which ethanol and ethanoic acid can be differentiated