Bihar Board Class 10 Science Solutions Chapter 4 Carbon and its Compounds

 

Bihar Board Class 10 Science Chapter 4 Carbon and its Compounds InText Questions and Answers

Intext Questions (Page 61)

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

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

Eight atoms (-S8 ) of sulphur molecule

Intext Questions (Page 68)

Question 1.
How many structural isomers can you draw for pentane ?
Answer:
We can draw three structural isomers of pentane ?

Question 2.
What are the two properties of carbon which lead to the huge number of carbon compound we see around us ?
Answer:
The two properties of carbon are –
(a) Catenation and (b) Tetra Covalency of carbon atom. Catenation is the uniqué property of carbon due to which carbon atoms can link among themselves to form a straight, banched or close chain. Due to tetravalency, the carbon atoms can form single, double or triple covalent bond. This is why carbon leads to the large number of compounds.

Question 3.
What will be the formula and electron dot structure of cyclopentane?
Answer:
The formula of cyclopentane is C5 H10

Question 4.
Draw the structure for the following compounds
(a) Etlianoic acid
(b) Bromopentane
(e) Butanone
(d) Hexanal.
Answer:

Question 5.
How would you name the following compound?

Answer:
(i) Bromo-ethane
(ii) Methanal
(iii) Hex 1-yne

Intext Questions (Page 71)

Question 1.
Why is the conversion of ethanol to ethanoie acid an oxidation reaction ?
Answer:

Here, in this reaction, there is a decrease in the number of hydrogen atoms in compound. Therefore, it is an oxidation reaction. Also number of oxygen atoms has increased.

Question 2.
A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not taken.
Answer:
Air contains nitrogen and other inactive gaseous contents which resist the sufficient supply of oxygen for burning of ethyne. So, air is not used for combustion of ethyne.

Intext Questions (Page 74)

Question 1.
How can you distinguish experimentally between an alcohol and a carboxylic acid.
Answer:
We can distinguish these two compounds by using laboratory reagent Na2CO3 (solution).
1. When Na2CO3is added to the test tube containing CH3COOH, CO2 gas is evolved, which turn lime water milky.
2. When Na2CO3 is added to the test tube containing CH3CH2OH then no gas is evolved.

Question 2.
What are oxidizing agents ?
Answer:
Oxidizing agents are the chemical substances which themselves ur aergo reduction and can oxidise the other species.
Example – KMNO4, and K2Cr2O7 are oxidising agents.

Intext Questions (Page 76)

Question 1.
Would you be able to check if water is hard by using a detergent ?
Answer:
No, it is impossible because detergent is effective in both hart) water and soft water.

Question 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:
By the reaction of soap with the calcium and magnesium salts, foam is formed^ This foam captures dust particles but also sticks to cloth To remove them from clotl, agitation is necessary.

Bihar Board Class 10 Science Chapter 4 Carbon and its Compounds Textbook Questions and Answers

Question 1.
Ethane, with the molecular formula – C2H6 – has
(a) 6 covalent bonds
(b) 7 covalent bonds
(c) 8 covalent bonds
(d) 9 covalent bonds.
Answer:
(b) 7 covalent bonds

Question 2.
Butanone is a four-carbon compound with the functional group –
(a) carboxylic acid
(b) aldehyde
(c) ketone
(d) alcohol.
Answer:
(c) ketone

Question 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.
Answer:
(b) the fuel is not burning completely.

Question 4.
Explain the nature of the covalent bond using the bond formation in CH3Cl.
Answer:
The bond line structure of CH3Cl is given as

Here 3-hydrogen atoms are linked with C-atom by single covalent bond. The bond between C and Cl atoms is covalent but due to higher value of electronegativity of Cl, the C-Cl bond is polar in nature.

Question 5.
Draw the electron dot structures for :
(a) ethanoic acid
(b) H2S
(c) propanone
(d) F2
Answer:
(a) Ethanoic acid

(b) H2S

(c) Propanone

(d) F2

Question 6.
What is- homologous series? Explain with examples.
Answer:
A group of compounds of carbon having same general formula and same functional group is called homologous series. The members of homologous series are called homologue. For example, alcohol.
(1) Methanol – CH3OH
(2) Ethanol – C2H5OH
(3) Propanol – C3H7OH
(4) Butanol – C4H9OH
Homologous series compounds have following characteristics :
(а) They have same general formula for all compounds.
(b) They have same functional group.
(c) They have same chemical but different physical property.
(d) They have difference of – CH2 between two successive members.
(e) Difference between masses of two successive member is 14 amu.

Question 7.
How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties ?
Answer:
Difference between ethanol and ethanoic acid :
Physical properties :
Ethanol

• It has a characteristic smell.
• Pure alcohol (95% or above) is called rectified alcohol.

Ethanoic acid :

• It has typical vinegar smell.
• Pure ethanoic acid is called glacial acetic acid.

Chemical properties:

Ethanol :
1. Ethanol does not react with NaOH.
C2H5OH + NaOH – No reaction.
2. Ethanol does not react with Na2CO3 solution.
C2H5 + Na2CO3 → No reaction
3. Ethanol on oxidation gives the ethanoic acid in presence of acidified KMnO4.

Ethanoic acid :

• Ethanojc acid reacts with XaOH1 to form sodium ethanoate. CH3COOH + NaOH → CH3COONa + H2O
• Ethandic acid reacts with Na2CO3 and gives CO2 gas. 2CH3COOH + Na2CO3 → 2CH2COONa + CO2 + H2O
• No. reaction with-acidified KMnO4.

Question 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 molecule consists of two parts – one part is hydrophobic and other part is hydrophilic. Hydrophobic part of soap is dissolved with dirt and hydrophilic part remains suspended in water. Thus, many more molecules of soap are attached to dirt having their one end suspended in water. So, micelle is formed. Since ethanol is not as polar as soaps, so, micelles will not be formed in other solvent such as ethanol also ?

Question 9.
Why are carbon and its compounds used as fuels for most applications ?
Answer:
Carbon and its compounds give large amount of heat on combustion due to high percentage of carbon and hydrogen. These compounds have optimum ignition temperature and are easy to handle. Their combustion can be controlled. Therefore, carbon and its compounds are used as a fuel.

Question 10.
Explain the formation of scum when hard water is treated with soap.
Answer:
Hard water contains soluble salts of Ca and Mg. When soap is dissolved in hard water, insoluble salts of Ca+2 and Mg+2  are formed which are called scum.

Question 11.
What change will you observe if you test soap with litmus paper (red and blue) ?
Answer:
The litmus paper will turn red due to the basic nature of soap.

Question 12.
What is hydrogenation ? What is its industrial application ?
Answer:
The addition of hydrogen to unsaturated hydrocarbon in the presence of a catalyst is called hydrogenation.

The reaction is extremely useful in the hydrogenation of oils. The edible oils which are used for cooking are mostly groundnut oil, cotton oil etc. These are unsaturated,compounds. These are hydrogenated to prepare solid fat which is known as vanaspati ghee in the industries.

Question 13.
Which of the following hydrocarbons undergo addition reactions :
C2H6, C3H8, C3H6, C2H2and CH4.
Answer:
Among the said hydrocarbons only C2H6 and C2H2 undergo addition reaction beacuse they are unsaturated hydrocarbons having double and triple bond between two carbon atoms respectively.

Question 14.
Give a test that can be used to differentiate chemically between butter and Rooking oil.
Answer:
Butter is a saturated fat so it does hot undergo catalytic hydrogenation but oil being unsaturated hydrocarbon can be hydrogenated in the presence of catalyst. Thus, the following reactions can be used to differentiate between butter and cooking oil.

Question 15.
Explain the mechanism of the cleaning action of soaps.
Answer:
Soap or detergent molecules are made up of two parts. One end is long hydrocarbon chain which is water repelling (hydrophobic). The other end is anion of carboxylic or sulphonic acid group which is water attracting (hydrophilic). So, when soap is dissolved in water, it forms groups of many molecules known as micelles as shown below. The tails stick inwards and S
the heads outwards. In the case of soap, negative end is – COO–
and in the case of detergent it is – SO23

These micelles dissolve oily droplets or dirt by the hydrophobic ends. When water is agitated, the oily dirt tends to lift off from the dirty surface and dissociates into fragments. This gives an opportunity to other tails to stick to oil.

The solution now contains small globules of oil surrounded by soap or detergent molecules. The negatively charged heads present in water prevent the small globules from coming together and form clusters. Thus, the oily dirt is removed from ,the object.

Bihar Board Class 10 Science Chapter 4 Carbon and its Compounds Textbook Activities

Activity 4.1 (Page 58)

Question 1.
Name ten things which you consume daily.
Answer:
Ten things are as below.
(1) food
(2) ink
(3) paper
(4) soap
(5) water
(6) polish
(7) salt
(8) oil
(9) cream
(10) milk.

Question 2.
List some items made up of metals.
Answer:
(a) Knife
(b) Steel glass
(c) Almirah
(d) Gas stove etc.

Question 3.
List some items which are compounds.
Answer:
(a) water
(b) cloth
(d) ink etc.

Question 4.
Name some compounds of carbon used in daily life.
Answer:
Sugar, tea, bread, ink, paper, oil, etc are the materials which are organic compounds and are used in our daily life.

Activity 4.2 (Page 67)

Question 1.
Calculate the difference in the formula and molecular masses for –
(a) CH3 OH and C2H5OH
(b) C3H5OH and C3H7OH
(c) C3H7OH and C4Hg OH
Answer:

Question 2.
Is there any similarity in these three ?
Answer:
All these three have alcoholic (- OH) functional group.

Question 3.
Arrange these alcohols in the order of increasing carbon atoms to get a family. Can we call this family a homologous series ?
Answer:
CH3OH, C2H5OH, C3H7OH, C4H9OH.
Yes, it is a homologous series of alkane alcohols.

Question 4.
Generate the homologous series for compounds containing up to four carbons for the other functional groups given in Table 4.3.
Answer:
Chloro (-Cl) → CH3Cl, C2H5Cl, C3H7Cl, C4H9Cl
Aldehydes → CH3CHO, C2H5CHO, C3H7 CHO, C4H9 CHO
Ketone → CH2CO, C2H4CO,C3H7CO, C4H8CO
Carboxylic acids CH3COOH, C2H3COOH, C3H7COOH, C4H9COOH

1. Homologous series having chloro (-Cl) functional group.
CH3Cl, C2H5Cl, C3H7Cl, C4H9Cl

2. Homologous series having aldehydes functional group.
CH3CHO, C2H5CHO, C3H7CHO, C4H9CHO

3. Homologous series having ketone functional group.
CH2CO, C2H4CO,C3H6CO, C4H8CO

4. Homologous series having carboxylic acids functional group.
CH3COOH, C2H3COOH, C3H7COOH, C4H9COOH

Question 5.
What is the difference between two successive members of a homologous series ?
Answer:
The two successive members ofhomologous series differ by CH2.

Question 6.
What is the difference of mass between two successive members of homologous series ?
Answer:
The masses of successive members of homologous series differ by 14 amu.

Question 7.
Write four members of homologous series having functional group – CHO.
Answer:
The members of homologous series are HCHO, CH3CHO, C2H5CHO, C3H7CHO.

Activity 4.3 (Page 69)

Question 1.
Place a metal plate above the flame. Is there a deposition on the plate in case of any of the compounds ?
Answer:
There is deposition in case of naphthalene and camphor on the plate.

Question 2.
Name the gases produced during combustion of an organic compound.
Answer:
CO2, H2O (vapour) are the gases which are produced during combustion of compounds of carbon.

Question 3.
What is the nature of flame when a saturated hydrocarbon is burnt ?
Answer:
Saturated hydrocarbons burn generally with clean blue flame in sufficient supply of air.

Question 4.
What is the nature of flame when an unsaturated hydrocarbon is burnt in air ?
Answer:
Combustion of unsaturated hydrocarbon will give a yellow flame With lots of black smoke.

Activity 4.4 (Page 69)

Question 1.
When do you get a yellow, sooty flame ?
Answer:
When there is insufficient supply of O2 and the carbon particles do not burn completely.

Question 2.
When do you get a blue flame ?
Answer:
When there is sufficient supply of O2 to burn carbon particles are completely burnt.

Question 3.
What is the function of hole at the bottom of bunsen burner ?
Answer:
With the help of hole at the bottom of the bunsen burner, we control the supply of air for the combustion.

Activity 4.5 (Page 70)

Question 1.
Does the colour of potassium permanganate persist when it is added initially ?
Answer:
The purple colour due to permanganate get decolourised during the reaction.

Question 2.
Why does the colour of potassium permanganate not disappear when excess is added ?
Answer:
When all the alcohol gets consumed the reaction stops and the purple colour persist.

Question 3.
What happens when ethanol is treated with 5% alkaline solution of KMNO4 ?
Answer:
The oxidation of ethanol takes place and ethanoic acid is formed.

Question 4.
What is the colour of potassium permanganate solution ?
Answer:
It is of purple colour.

Question 5.
What is the nature of potassium permanganate ?
Answer:
Potassium permanganate is a powerful oxidizing agent.

Activity 4.6 (Page 72)

Question 1.
What do you observe ?
Answer:
Na metal, being highly reactive, reacts with ethanol to give hydrogen gas and sodium ethoxide.
2C2H5OH + 2Na → 2C2H5ONa + H2

Question 2.
How will you test the gas evolved ?
Answer:
A burning splitter is bought near to the gas and the gas bums with pop sound. The product formed is water. Therefore the gas evolved is H2 (gas).
2H2 + O2 →2H2O

Question 3.
What is absolute alcohol ?
Answer:
98% to 100% ethanol is called absolute alcohol.

Activity 4.7 (Page 73)

Question 1.
Are both acids indicated by the litmus test ?
Answer:
Yes.

Question 2.
Does the universal indicator show them as equally strong acids ?
Answer:
No.

Question 3.
What is the pH of acids ?
Answer:
pH for acid is less than 7.

Question 4.
What is the pH of nutral solution.
Answer:
pH of a neutral solution is 7.

Question 5.
What is the pH of bases ?
Answer:
pH of bases is more than 7 and less than 14.

Question 6.
What is universal indicator ?
Answer:
Universal indicator is a chemical substance which has a particular colour in a solution of fixed pH.

Activity 4.8 (Page 73)

Questions Based on the Activity

Question 1.
Which one is stronger Acid, HCl or ethanoic acid ?
Answer:
Ethanoic acid is weaker acid than HCl as pH of HCl is less than the pH of ethanoic acid.

Question 2.
What is glacial acetic acid ?
Answer:
100% pure acetic acid is called glacial acetic acid.

Question 3.
Name the reaction which takes place between glacial acetic acid and absolute alcohol.
Answer:
It is called esterification.

Activity 4.9 (Page 74)

Question 1.
What do you observe ?
Answer:
Following reaction takes place :

i.e. sodiums acetate is formed.

Question 2.
Pass the gas produced through freshly prepared lime-water. What do you observe ?
Answer:
The lime-water turns milky.

Question 3.
Can the gas produced by the reaction between ethanoic acid and sodium carbonate be identified by this ‘ test”?
Answer:
Yes,, the gas turns the lime-water milky. That means ’ the gas produced is CO2.

Question 4.
Write the formula of sodium carbonate and also state whether its water solution is acidic or basic.
Answer:
Na2CO3 is formula of sodium carbonate. The Na2CO3 solution is basic in nature.

Question 5.
What happens when sodium carbonate is treated with ethanoic acid ?
Answer:
When sodium carbonate is treated with ethanoic acid, reaction takes place with effervescence and CO2 gas is evolved.

Question 6.
What happens when gas evolved is passed through a lime water (In above question)
Answer:
The lime water becomes milkly due to formation of CaCO3 particle.

Question 7.
Write the chemical reaction between sodium hydrogen carbonate and ethanoic acid.
Answer:

Activity 4.10 (Page 74)

Question 1.
Can you see the oil and water layers separately – in both the test tubes immediately after you stop shaking,
them ?
Answer:
No, It is not clear.

Question 2.
Leave the test tubes undisturbed for some time and observe. Does the oil layer separate out ? In which test tube does this happen first ?
Answer:
In test tube A the oil layer separate out. In test tube A, it happens first.

Question 3.
Is oil drop miscible in water ?
Answer:
No, oil drop is not miscible in water.

Question 4.
Take a test tube. Add a drop of oil in it. Add a piece of soap in it and shake it properly. Whether the oil droplets would appear again or disappear ?
Answer:
Oil droplets disappear as these are acted upon by soap ! to form sodium salt of fatty acid.

Question 5.
What are soaps ?
Answer:
Soaps are sodium salt of fatty acid.
Example : C17H35COONa (sodium stearate).

Activity 4.11 (Page 76)

Question 1.
In which test tube do you get more foam ?
Answer:
The test tube containing distilled water has more foam.

Question 2.
In which test tube do you observe a white curdy precipitate ?
Answer:
In the test tube containing hard water.

Question 3.
What is hard water ?
Answer:
A water containing soluble salts of Mg+2 and Ca+2 is a hard water.

Question 4.
Why does not soap form lather with hard water ?
Answer:
Soap reacts with hard water to form scum and acts to ; remove the hardness of water. So, lather is riot formed with hard ; water and soap.

Question 5.
Name one pure form of water present in nature.
Answer:
Rain water is the purest form of water which is found in nature.

Question 6.
What is scum ?
Answer:
When soap reacts with soluble salts of hard water, a white precipitate is formed which is called scum.

Activity 4.12 (Page 76)

Question 1.
Do both test tubes have the same amount of foam ?
Answer:
No, the test tube to which detergent was added has more foam.

Question 2.
In which test tube is a curdy solid formed ?
Answer:
In the test tube in which soap was added.

Question 3.
What are detergents ?
Answer:
Synthetic detergents are sodium salts of sulphoric acid group (- S03Na) attached to a long chain of hydrocarbon.

Question 4.
Which will form foam with hard water easily soap or synthetic detergent ?
Answer:
Synthetic detergent will form foam more easily with hard water as it does not react with the soluble salts of Mg and Ca present in hard water.

Question 5.
Why is detergent a better cleansing agent than soap ?
Answer:
Detergent is a cleansing agent better than soap because detergent acts better even in hard water.

Question 6.
Which causes water pollution, detergent or soap ?
Answer:
Detergent causes water pollution as detergents are non-biodegradable.

Bihar Board Class 10 Science Chapter 4 Carbon and its Compounds NCERT Exemplar Problems

Short Answer Type Questions

Question 1.
Draw the electron dot structure of ethyne and also draw its structural formula.
Answer:
H : C :: C : H Electron dot structure of ethyne (C2H2)
H – C = C – H Structural formula of ethyne

Question 2.
Write the names of the following compounds

Answer:
(a) Pentanoic acid
(b) Butyne
(c) Heptanal
(d) Pentanol

Question 3.
Identify and name the functional groups present in the following compounds.

Answer:

Question 4.
A compound X is formed by the reaction of a carboxylic acid C2H4O2 and an alcohol in presence of a few drops of H2SO4. The alcohol on oxidation with alkaline KMnO4 followed by acidification gives the same carboxylic acid as used in this reaction. Give the names and structures of (a) carboxylic acid, (6) alcohol and (c) the compound X. Also write the reaction.
Answer:
(a) Carboxylic acid is ethanoic acid
(b) Alcohol is ethanol
(c) X is ethyl ethanoate

Question 5.
Why detergents are better cleansing agents than soaps? Explain.
Answer:
Detergents work as a cleansing agent both in hard and soft water. The charged ends of detergents do not form insoluble precipitates with calcium and magnesium ions in hard water and hence removes the dirt easily. But it is hot the case with soaps. Thus, detergents are better cleansing agents than soaps.

Question 6.
Name the functional groups present in the following compounds
(a) CH3COCH2CH2CH2CH3
(b) CH3CH2CH2COOH
(c) CH3CH2CH2CH2CHO
(d)CH3CH2OH
Answer:
(a) Ketone
(b) Carboxylic acid
(c) Aldehyde
(d) Alcohol

Question 7.
How is ethene prepared from ethanol? Give the reaction involved in it.
Answer:
Heating of ethanol with excess concentrated sulphuric acid at 443 K results in its dehydration to give ethene.

Question 8.
Intake of small quantity of methanol can be lethal. Comment.
Asn. Methanol is oxidised to methanal in the liver. Methanal reacts rapidly with the components of cells. It causes the protoplasm to coagulate. It also affects the optic nerve, causing blindness. That is why intake of small quantity of methanol can be lethal,

Question 9.
A gas is evolved when ethanol reacts with sodium. Name the gas evolved and also write the balanced chemical equation of the reaction involved.
Answer:
Gas evolved is hydrogen.
2CH3CH2OH + 2Na → 2CH3CH2O–Na++ H2

Question 10.
Ethene is formed when ethanol at 443 K is heated with excess of concentrated sulphuric acid. What is the role of sulphuric acid in this reaction? Write the balanced chemical equation of this reaction.
Answer:
Sulphuric acid acts as a dehydrating agent.

Question 11.
Carbon, Group (14) element in the Periodic Table, is known to form compounds with many elements.
Write an example of a compound formed with
(а) chlorine (Group 17 of Periodic Table)
(b) oxgygen (Group 16 of Periodic Table)
Answer:
(a) Carbon tetrachloride (CC l4)
(b) Carbon dioxide (CO2)

Question 12.
In electron dot structure, the valence shell electrons are represented by crosses or dots.
(а) The atomic number of chlorine is 17. Write its electronic configuration .
(b) Draw the electron dot structure of chlorine molecule.
Answer:
(a) K; L, M
2, 8, 7

Question 13.
Catenation is the ability of an atom to form bonds with other atoms of the same element. It is exhibited by both carbon and silicon. Compare the ability of catenation of the two elements. Give reasons.
Answer:
Carbon exhibits catenation,much more than silicon or any other element due to its smaller size which makes the C – C bonds strong while the Si – Si bonds are comparatively weaker due to its large size.

Question 14.
Unsaturated hydrocarbons contain multiple bonds between the two C – atoms and show addition , reactions. Give the test to distinguish ethane from ethene.
Answer:
Ethane is a saturated hydrocarbon and ethene is an unsaturated hydrocarbon: The two can be distinguished by subjecting them to the flame. Ethane gives a clear flame while ethene gives a yellow flame with lots of black smoke.

Question 15.
Match the reactions given in Column (A) with I the names given in Column (B).

Answer:
(a) – (iv) (b) – (i)
(c) – (ii) (d) – (iii)

Question 16.
Write the structural formulae of all the isomers of fiexane.
Answer:

Question 17.
What is the role of metal or reagents written on arrows in the given chemical reactions?

Answer:
(a) Ni acts as a catalyst.
(b) Concentrated H2SO4 acts as a catalyst.
(c) Alkaline KMnO4 acre as an oxidising agent.

Long Answer Type Questions

Question 18.
A salt X is formed and a gas is evolved when ethanoic acid reacts .with sodium hydrogencarbonate. Name the salt X and the gas evolved. Describe an activity and draw the diagram of the apparatus to prove that the evolved gas is the one which you have named. Also, write chemical equation of the reaction involved.
Answer:
When ethanoic acid reacts with sodium hydrogen carbonate, sodium ethanoate (X) is formed and carbon dioxide gas is evolved.

Activity to prove that the evolved gas is carbon dioxide.

It is the characteristic property of CO2 that it turns lime water milky. So, to prove that the gas evolved in the above reaction is CO2, we will pass it through lime water. Set up the apparatus as shown in the figure and observe the colour of the lime water. As soon as the reaction between CH3COOH and NaHCO3 gets completed and the gas evolved during this reaction passes through lime water, it turns milky, proving that the gas evolved is CO2.
The involved reaction is :

Question 19.
(a) What are hydrocarbons? Give examples.
(b) Give the structural differehces between saturated and unsaturated hydrocarbons with two examples each.
(c) What is a functional group? Give examples of four different functional groups.
Answer:
(a) Compounds of carbon and hydrogen are called hydrocarbons. Examples methane (CH4), ethane (C2H6) etc.
(b) Saturated hydrocarbons contain carbon-carbon single bonds. ,
Unsaturated hydrocarbons contain atleast one carbon – carbon double or triple boncf.

(c) Functional group – An atom/group of atoms joined in a specific manner which is responsible for the characteristic chemical properties of the organic compounds. Examples are ’ hydroxyl group (- OH), aldehyde group (- CHO), carboxylic group (- COOH) etc.

Question 20.
Name the reaction which is commonly used in the conversion of vegetable oils to fats. Explain the I) reaction involved in detail.
Answer:
The reaction which is commonly used in the conversion of vegetable oils to fats is called hydrogenation reaction. During hydrogenation, the addition of hydrogen to unsaturated 1 hydrocarbon in the presence of a catalyst takes place. The edible oils which are used for cooking are mostly groundnut oil, cotton seed oil, sunflower oil, etc. generally have long unsaturated carbon chains. These are hydrogenated to prepare solid fat which is known as vanaspati ghee.

Question 21.
(a) Write the formula and draw electron dot structure of carbon tetrachloride.
(b) What is saponification? Write the reaction ; involved in this process.
Answer:
(a) Formula of carbon tetrachloride is CCl4.
The electron dot structure of CCl4 is given below :

(b) Saponification is the process of converting esters into salts of carboxylic acids and parent alcohol by treating them with a base.

Question 22.
Esters are sweet-smelling substances and are used in making perfumes. Suggest some activity and the reaction involved for the preparation of an ester with well labelled diagram.
Answer:
Activity :
Take 1 mL ethanol (absolute alcohol) and 1 mL glacial acetic acid along with a few drops of concentrated sulphuric acid in a test tube.
Warm in a water-bath at about 60°C for at least 15 minutes as shown in ,The figure (It should not be heated directly on flame as the vapours of ethanol catch fire).

Pour into a beaker containing 20 – 50 mL of water and smell the resulting mixture.

Question 23.
A compound C (molecular formula C2H4O2) reacts with Na-metal to form a compound R and evolves a gas which burns with a pop sound. Compound C on treatment with an alcohol A in presence of an acid forms ‘ a sweet smelling compound S (molecular formula – C3H6O2). On addition of NaOH to C, it also gives R and water. S on treatment with NaOH solution gives back R and A.
Identify C, R, A, S and write down the reactions involved.
Answer:
C – Ethanoic acid
R – Sodium salt of ethanoic acid (sodium acetate) and gas evolved is hydrogen
A – Methanol
S – Ester (Methyl acetate)

Question 24.
Look at given figure and answer the following questions
(a) What change would you observe in the calcium hydroxide solution taken in tube B?
(b) Write the reaction involved in test tubes A and B respectively.
(c) If ethanol is given instead of ethanoic acid, would you expect the same change?
(d) How can a solution of lime water be prepared in the laboratory ?.

Answer:
(a) It will turn milky.
(b) 2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2 (Test tube A)
Ca(OH)2 + CO2 → CaCO3 + H2O (Test tube B)
With excess CO2 milkiness disappears.
CaCO3 + H2O + CO2 → Ca(HCO3)2
(c) As C2H5OH and Na2CO3 do not react, a similar change is not expected.
C2H5OH + Na2CO3 → No change

(d) The lime water is prepared by dissolving calcium oxide in water and decanting the supernatent liquid.

Question 25.
How would you bring about the following conversions? Name the process and write the reaction involved.
(a) ethanol to ethene.
(b) propanol to propanoic acid.
Answer:
(a) By the dehydration of ethanol in the presence of concentrated H2SO4.

Dehydration of ethanol : Heating ethanol at 443 K with excess cone. H2SO4 results in the dehydration of ethanol to give ethene.

(b) By the oxidation of propanol using oxidising agent such as alkaline KMn04.

Question 26.
Draw the possible isomers of the compound with molecular formula C3H6O and also give their electron dot structures.
Answer:

Question 27.
Explain the given reactions with the examples
(а) Hydrogenation reaction
(b) Oxidation reaction
(c) Substitution reaction
(d) Saponification reaction
(e) Combustion reaction
Answer:
(a) Hydrogenatioh reaction : The addition of hydrogen to unsaturated hydrogen in the presence of a catalyst is called hydrogenation reaction.
For example :

(b) Oxidation reaction : The reaction in which gain of oxygen takes place is called an oxidation reaction.
For example : Oxidation of ethanol to ethanoic acid takes place in the presence of alkaline KMn04 on heating. ,

(c) Substitution reaction : The reaction in which one type of atom or a group of atoms takes the place of other is called a substitution reaction.
For example : In the presence of sunlight, chlorine is added to hydrocarbons.

(d) Saponification reaction : Saponification is the process of converting esters into salts of carboxylic acids and the parent
alcohol by treating them with a base. It is called so because it is used in the preparation of soaps.
For example :

(e) Combustion reaction : When a carbon Containing compound is burnt, a large amount of heat and light is released. This reaction is called combustion reaction.

For example : When methane burns to produce CO2 and water, a large amount of heat and light is produced.
CH4 + 2O2 → CO2 + 2H2O + Heat and light

Question 28.
An organic compound A on heating with concentrated H2SO4 forms a compound B which on – addition of one mole of hydrogen in presence of Ni forms a compound C. One mole of compound C on combustion forms two moles of CO2 and 3 moles of H2O. Identify the compounds A, B and C and write the chemical equations of the reactions involved.
Answer:
Since compound C gives 2 moles of CO2 and 3 moles of H2O, it shows that it has the molecular formula: C2H6 (Ethane). C is obtained by the addition of one mole of hydrogen to compound B so the molecular formula of B should be C2H4 (Ethene). Compound B is obtained by heating compound A with concentrated H2SO4 which shows it to be an alcohol. So compound A codld be C2H4OH (Ethanol)