2nd Year Chemistry Chapter 8 (Aliphatic Hydrocarbons) Online Preparation

Online Short Questions For Chapter 8 "12th Class Chemistry Chapter 8 Short Questions Preparation "

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Chemistry - 12th Class Chemistry Chapter 8 Short Questions Preparation

Question # 1

Give three use of methane?

Ans 1:
- Methane is used as fuel as an illuminating gas.
- used for the preparation of methyl chloride ,methylene chloride,chloroform.
- for the preparation of carbon black used in paints ,prints printing inks and automobiles tyres.

Question # 2

What is Hydrogenolysis?Give an example.

Ans 1: Hydrogenolysis is a chemical reaction whereby a carbon -carbon or carbon-heteroatom single bond is cleaved or undergoes lysis by hydrogen.The heteroatom may vary,but it usually is oxygen,nitrogen or sulfur.A related reaction is hydrogenation,where hydrogen is added to the molecule,without cleaving bonds.
R-X + H-H-----> R-H + HX

Question # 3

Explain Markovnikov rule with one example,

Ans 1: In the addition of an unsymmetrical reagent to an unsymmetrical alkene the negative part of the adding reagent goes to that carbon,constituting the double bond which has least number of hydrogen atom is called Markovnikov rule.

Question # 4

The sigma bonds are inert in alkanes.Explain?

Ans 1: In the alpha bond the electrons are very tightly held between the nuclei which make it very stable bond,A lot of energy is required to break it.The alkanes or paraffins under ordinary condition are inert towards acid,alkalis,oxidizing and reducing agents.

Question # 5

Define Ramy nickel.Give its use.

Ans 1: Rany nickel is a catalyst which is prepared by treating a Ni-Al alloy with caustic soda.Most alkanes are hydrogenated over Raney nickel at about 100 degree and upto 3-atmosphere pressure.

Question # 6

Describe nitration of methane.

Ans 1: It is substitution reaction of alkanes in which a hydrogen atom of an alkane is replaced by nitro group .Alkanes undergo vapour -phase nitration under dractic condition to give nitroalkanes.

Question # 7

Alkanes are less reactive than alkenes. Comment?

Ans 1: The alkanes or paraffins(Latin: parum=little,affins=affinity) under ordinary condition are inert towards acids,alkalis,oxidizing and reducing agents.The un-reactivity of alkanes can also be explained on the basis of inertness of a o-bond.In a o-bond the electrons are very tightly held between the nuclei which makes it is very stable bond.A lot of energy is required to break it.
Ans 2: On the other hand alkenes contains sigma-bond,having partially filled p-orbitals overlap in a parallel fashion.sigma-electron are less firmly held between the nulei. In alkenes a sigma-bond is,therefore,a weak bond as compared to a o-bond.

Question # 8

Why ethene is more reactive than ethyne towards additions reactions?

Ans 1: Ethene contains sigma-bond having partially filled p-orbitals overlap in a parallel fashion.sigma-electrons are less firmly held between the nulei. In ethene a sigma-bond is a weak bond.
Ans 2: In ethyne,the carbon atoms are held together by a triple bond,a 0-bond and two sigma-bond.The electrons density between the carbon atoms is very high which draws atoms very close to each other.Electrons in a triple bond are,therefore,less exposed and thus less reactive reagents.

Question # 9

Identify the actual product ,when HBr is added to propene.

Ans 1: Propene is an unsymmetrical alkene,According to Markovnikov rule.the negative part of the adding reagent goes to that carbon,constituting the double bond,which has least number of hydrogen atom.

Question # 10

Distinguish between Ethene and Acetylene?

Ans 1: Ethene and acetylene both are un-saturated compounds. Ethene contains sigma-bond,having partially fiiled p-orbitals overlap in a parallel fashion.sigma-electron are less firmly held between the nuclie. In ethene a sigma-bond is a weak bond.
Ans 2: In actetylene,the carbon atoms are held together by a triple bond,a o-bond and two sigma-bond.The electron density between the carbon atoms is very high which draws atoms very close to each other.Electron in a triple bond are,therefore,less exposed and thus less reactive towards reagents than ethene.

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Prepare Complete Set Wise Questions For Chapter 8 "12th Class Chemistry Chapter 8 Short Questions Preparation "

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Set 2

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12th Class Chemistry Chapter 8 Short Questions Preparation - Set 1

Question # 1

Give three use of methane?

Ans 1:
- Methane is used as fuel as an illuminating gas.
- used for the preparation of methyl chloride ,methylene chloride,chloroform.
- for the preparation of carbon black used in paints ,prints printing inks and automobiles tyres.

Question # 2

What is Hydrogenolysis?Give an example.

Ans 1: Hydrogenolysis is a chemical reaction whereby a carbon -carbon or carbon-heteroatom single bond is cleaved or undergoes lysis by hydrogen.The heteroatom may vary,but it usually is oxygen,nitrogen or sulfur.A related reaction is hydrogenation,where hydrogen is added to the molecule,without cleaving bonds.
R-X + H-H-----> R-H + HX

Question # 3

Explain Markovnikov rule with one example,

Ans 1: In the addition of an unsymmetrical reagent to an unsymmetrical alkene the negative part of the adding reagent goes to that carbon,constituting the double bond which has least number of hydrogen atom is called Markovnikov rule.

Question # 4

The sigma bonds are inert in alkanes.Explain?

Ans 1: In the alpha bond the electrons are very tightly held between the nuclei which make it very stable bond,A lot of energy is required to break it.The alkanes or paraffins under ordinary condition are inert towards acid,alkalis,oxidizing and reducing agents.

Question # 5

Define Ramy nickel.Give its use.

Ans 1: Rany nickel is a catalyst which is prepared by treating a Ni-Al alloy with caustic soda.Most alkanes are hydrogenated over Raney nickel at about 100 degree and upto 3-atmosphere pressure.

Question # 6

Describe nitration of methane.

Ans 1: It is substitution reaction of alkanes in which a hydrogen atom of an alkane is replaced by nitro group .Alkanes undergo vapour -phase nitration under dractic condition to give nitroalkanes.

Question # 7

Alkanes are less reactive than alkenes. Comment?

Ans 1: The alkanes or paraffins(Latin: parum=little,affins=affinity) under ordinary condition are inert towards acids,alkalis,oxidizing and reducing agents.The un-reactivity of alkanes can also be explained on the basis of inertness of a o-bond.In a o-bond the electrons are very tightly held between the nuclei which makes it is very stable bond.A lot of energy is required to break it.
Ans 2: On the other hand alkenes contains sigma-bond,having partially filled p-orbitals overlap in a parallel fashion.sigma-electron are less firmly held between the nulei. In alkenes a sigma-bond is,therefore,a weak bond as compared to a o-bond.

Question # 8

Why ethene is more reactive than ethyne towards additions reactions?

Ans 1: Ethene contains sigma-bond having partially filled p-orbitals overlap in a parallel fashion.sigma-electrons are less firmly held between the nulei. In ethene a sigma-bond is a weak bond.
Ans 2: In ethyne,the carbon atoms are held together by a triple bond,a 0-bond and two sigma-bond.The electrons density between the carbon atoms is very high which draws atoms very close to each other.Electrons in a triple bond are,therefore,less exposed and thus less reactive reagents.

Question # 9

Identify the actual product ,when HBr is added to propene.

Ans 1: Propene is an unsymmetrical alkene,According to Markovnikov rule.the negative part of the adding reagent goes to that carbon,constituting the double bond,which has least number of hydrogen atom.

Question # 10

Distinguish between Ethene and Acetylene?

Ans 1: Ethene and acetylene both are un-saturated compounds. Ethene contains sigma-bond,having partially fiiled p-orbitals overlap in a parallel fashion.sigma-electron are less firmly held between the nuclie. In ethene a sigma-bond is a weak bond.
Ans 2: In actetylene,the carbon atoms are held together by a triple bond,a o-bond and two sigma-bond.The electron density between the carbon atoms is very high which draws atoms very close to each other.Electron in a triple bond are,therefore,less exposed and thus less reactive towards reagents than ethene.

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12th Class Chemistry Chapter 8 Short Questions Preparation - Set 2

Question # 1

Give three use of methane?

Ans 1:
- Methane is used as fuel as an illuminating gas.
- used for the preparation of methyl chloride ,methylene chloride,chloroform.
- for the preparation of carbon black used in paints ,prints printing inks and automobiles tyres.

Question # 2

Why are alkenes also called olefins?

Ans 1: Alkenes also known as olefins(derived from Latin word olefiant meaning oil forming ) because its lower members from oily products on treatment with chlorine or bromine.

Question # 3

Mention four uses of ethene.

Ans 1: i) For the manufacture of polythene,a plastic material used of making toys,cables,bags,boxes etc.
Ans 2: ii) For a artificial ripening of the fruits.
Ans 3: iii) As a general anesthetic.
Ans 4: iv) For preparing Mustard gas a chemical used in Word War I,the name comes from its mustard like odour,it is not a gas,but a high boiling liquid that is dispersed as a mist of tiny droplest.

Question # 4

What is Hydrogenolysis?Give an example.

Ans 1: Hydrogenolysis is a chemical reaction whereby a carbon -carbon or carbon-heteroatom single bond is cleaved or undergoes lysis by hydrogen.The heteroatom may vary,but it usually is oxygen,nitrogen or sulfur.A related reaction is hydrogenation,where hydrogen is added to the molecule,without cleaving bonds.
R-X + H-H-----> R-H + HX

Question # 5

Describe a test for the presence of unsaturation in organic molecules.

Ans 1: When alkenes are treated with mild oxidizing reagents like dilute alkaline KMnO₄solution (Bayer's Reagent) at low temperature,hydroxylation of double bond occur resulting in the formation of dihydroxy compounds known as vicinal glycols. The pink colouration of KMnO₄solution is discharged.
3CH₂=CH₂+ 2KMnO₄+ 4H₂O---->HO-CH₂-CH₂-OH+2MnO₂+2KOH

Question # 6

Why Alkynes are less reactive than alkenes towards Electrophilic Regents?

Ans 1: A sigma-bond in alkenes is not only weak but its electrons are more expose to an attack by an electrophilic reagent.Both these acts make the alkenes a very reactive class of compounds. Alkynes although contain two sigma-bond are less reactive than alkenes towards electrophilic reagents this is because the bond distance between the two triple bonded carbon atoms is very short and hence the sigma-electrons are not available to be attacked by electrophilic reagents.

Question # 7

The sigma bonds are inert in alkanes.Explain?

Ans 1: In the alpha bond the electrons are very tightly held between the nuclei which make it very stable bond,A lot of energy is required to break it.The alkanes or paraffins under ordinary condition are inert towards acid,alkalis,oxidizing and reducing agents.

Question # 8

Describe nitration of methane.

Ans 1: It is substitution reaction of alkanes in which a hydrogen atom of an alkane is replaced by nitro group .Alkanes undergo vapour -phase nitration under dractic condition to give nitroalkanes.

Question # 9

How ethene can be prepared by Kolb's electrolysis?

Ans 1: When a concentrated solution of sodium or potassium of a monocarboxylic acid is electrolyzed an alkane is produced this method is only suitable foe the preparation of symmetrical alkanes.

Question # 10

Write structural formulas for two compound;i) Vinyl acetylene ii) But-3-en-yne

Ans 1: i) Vinyl acetylene: CH₂=CH-C=CH
Ans 2: ii) 1-Butene-3-yne: CH₂=CH-C=CH

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12th Class Chemistry Chapter 8 Preparation

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2nd Year Chemistry Chapter 8 (Aliphatic Hydrocarbons) Online Preparation

Online Short Questions For Chapter 8 "12th Class Chemistry Chapter 8 Short Questions Preparation "

Chemistry - 12th Class Chemistry Chapter 8 Short Questions Preparation

Give three use of methane?

What is Hydrogenolysis?Give an example.

Explain Markovnikov rule with one example,

The sigma bonds are inert in alkanes.Explain?

Define Ramy nickel.Give its use.

Describe nitration of methane.

Alkanes are less reactive than alkenes. Comment?

Why ethene is more reactive than ethyne towards additions reactions?

Identify the actual product ,when HBr is added to propene.

Distinguish between Ethene and Acetylene?

Prepare Complete Set Wise Questions For Chapter 8 "12th Class Chemistry Chapter 8 Short Questions Preparation "

Set 1

Set 2

12th Class Chemistry Chapter 8 Short Questions Preparation - Set 1

Give three use of methane?

What is Hydrogenolysis?Give an example.

Explain Markovnikov rule with one example,

The sigma bonds are inert in alkanes.Explain?

Define Ramy nickel.Give its use.

Describe nitration of methane.

Alkanes are less reactive than alkenes. Comment?

Why ethene is more reactive than ethyne towards additions reactions?

Identify the actual product ,when HBr is added to propene.

Distinguish between Ethene and Acetylene?

12th Class Chemistry Chapter 8 Short Questions Preparation - Set 2

Give three use of methane?

Why are alkenes also called olefins?

Mention four uses of ethene.

What is Hydrogenolysis?Give an example.

Describe a test for the presence of unsaturation in organic molecules.

Why Alkynes are less reactive than alkenes towards Electrophilic Regents?

The sigma bonds are inert in alkanes.Explain?

Describe nitration of methane.

How ethene can be prepared by Kolb's electrolysis?

Write structural formulas for two compound;i) Vinyl acetylene ii) But-3-en-yne

12th Class Chemistry Chapter 8 Preparation

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