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

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 # 2

How common name of alkenes are derived?Give common names of CH₂=CH₂and CH₃-CH₂=CH_2?

Ans 1: For alkanes the word is derived from the Greek or Latin numerals indicating the number of carbons atom in molecule and the name is completed by adding ane as a suffix.Alkenes are similarly named by replacing the ending "ane" of the name of alkane with "ylene".

Question # 3

How can ethyne be prepared commercially from calcium carbide?

Ans 1: On industrial scale ethyne is prepared by the reaction of calcium carbide (CaC₂) with water.Calcium carbide is prepared by heating lime (CaO) and coke (C) at a very high temperature in an electric furnace.
CAO + C------>CaC₂+ CO
CaC₂+2H₂O------->Ca(OH)₂+ HC=CH

Question # 4

Explain acidic nature of ethyne?

Ans 1: Ethnelnethyne,the hydrogen atom is bonded to the carbon atom with sp-s overlap.The sp hybridized carbon atom of ethyne pulls the electrons more strongly making the attached hydrogen atom slightly acidic as:H-C=C^-8-H⁺⁸

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

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.

Question # 7

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 # 8

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 # 9

What is heat of combustion?

Ans 1: Burning of alkane in presence of oxygen is known as combustion,Complete combustion of an alkene yield CO₂,H₂O and heat.The amount to heat evolved when one mole of a hydrocarbon is brunt to CO₂and H₂O is called heat of combustion.

Question # 10

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.

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

Set 1

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Set 2

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

Question # 1

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 # 2

How common name of alkenes are derived?Give common names of CH₂=CH₂and CH₃-CH₂=CH_2?

Ans 1: For alkanes the word is derived from the Greek or Latin numerals indicating the number of carbons atom in molecule and the name is completed by adding ane as a suffix.Alkenes are similarly named by replacing the ending "ane" of the name of alkane with "ylene".

Question # 3

How can ethyne be prepared commercially from calcium carbide?

Ans 1: On industrial scale ethyne is prepared by the reaction of calcium carbide (CaC₂) with water.Calcium carbide is prepared by heating lime (CaO) and coke (C) at a very high temperature in an electric furnace.
CAO + C------>CaC₂+ CO
CaC₂+2H₂O------->Ca(OH)₂+ HC=CH

Question # 4

Explain acidic nature of ethyne?

Ans 1: Ethnelnethyne,the hydrogen atom is bonded to the carbon atom with sp-s overlap.The sp hybridized carbon atom of ethyne pulls the electrons more strongly making the attached hydrogen atom slightly acidic as:H-C=C^-8-H⁺⁸

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

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.

Question # 7

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 # 8

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 # 9

What is heat of combustion?

Ans 1: Burning of alkane in presence of oxygen is known as combustion,Complete combustion of an alkene yield CO₂,H₂O and heat.The amount to heat evolved when one mole of a hydrocarbon is brunt to CO₂and H₂O is called heat of combustion.

Question # 10

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.

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

Question # 1

What is effect of branching on boiling of alkanes?

Ans 1: The boiling points of alkanes having branced chain structure are lower than their isomeric normal chain alkanes,e.g n-butane has higher boiling point than isobutene.

Question # 2

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 # 3

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 # 4

How common name of alkenes are derived?Give common names of CH₂=CH₂and CH₃-CH₂=CH_2?

Ans 1: For alkanes the word is derived from the Greek or Latin numerals indicating the number of carbons atom in molecule and the name is completed by adding ane as a suffix.Alkenes are similarly named by replacing the ending "ane" of the name of alkane with "ylene".

Question # 5

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 # 6

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 # 7

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 # 8

How can ethyne be prepared commercially from calcium carbide?

Ans 1: On industrial scale ethyne is prepared by the reaction of calcium carbide (CaC₂) with water.Calcium carbide is prepared by heating lime (CaO) and coke (C) at a very high temperature in an electric furnace.
CAO + C------>CaC₂+ CO
CaC₂+2H₂O------->Ca(OH)₂+ HC=CH

Question # 9

Explain acidic nature of ethyne?

Ans 1: Ethnelnethyne,the hydrogen atom is bonded to the carbon atom with sp-s overlap.The sp hybridized carbon atom of ethyne pulls the electrons more strongly making the attached hydrogen atom slightly acidic as:H-C=C^-8-H⁺⁸

Question # 10

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.

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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

Define Ramy nickel.Give its use.

How common name of alkenes are derived?Give common names of CH2=CH2and CH3-CH2=CH2?

How can ethyne be prepared commercially from calcium carbide?

Explain acidic nature of ethyne?

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

Distinguish between Ethene and Acetylene?

Why Alkynes are less reactive than alkenes towards Electrophilic Regents?

How ethene can be prepared by Kolb's electrolysis?

What is heat of combustion?

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

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

Define Ramy nickel.Give its use.

How common name of alkenes are derived?Give common names of CH2=CH2and CH3-CH2=CH2?

How can ethyne be prepared commercially from calcium carbide?

Explain acidic nature of ethyne?

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

Distinguish between Ethene and Acetylene?

Why Alkynes are less reactive than alkenes towards Electrophilic Regents?

How ethene can be prepared by Kolb's electrolysis?

What is heat of combustion?

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

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

What is effect of branching on boiling of alkanes?

Describe nitration of methane.

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

How common name of alkenes are derived?Give common names of CH2=CH2and CH3-CH2=CH2?

Alkanes are less reactive than alkenes. Comment?

The sigma bonds are inert in alkanes.Explain?

How ethene can be prepared by Kolb's electrolysis?

How can ethyne be prepared commercially from calcium carbide?

Explain acidic nature of ethyne?

Mention four uses of ethene.

12th Class Chemistry Chapter 8 Preparation

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How common name of alkenes are derived?Give common names of CH₂=CH₂and CH₃-CH₂=CH_2?

How common name of alkenes are derived?Give common names of CH₂=CH₂and CH₃-CH₂=CH_2?

How common name of alkenes are derived?Give common names of CH₂=CH₂and CH₃-CH₂=CH_2?