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

Question # 1

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 # 2

Ans 1: Hydrogenation is a process in which molecule of hydrogen added to an alkene in the presence of a catalyst and at moderate pressure (1-5 atm ) to give a saturated compound.

Question # 3

Ans 1: In the formation of pie bond,the partially filled p-orbitals overlap in a parallel fashion,the probability of finding electron is thus away from the line joining the two nuclei,due to this reason pei electron are less fimely helf between the nuclei.

Question # 4

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 # 5

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 # 6

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 # 7

Ans 1: Those compounds in which the four valencies of carbons are satisfied by single bonds to either other carbon atom or hydrogen atom are called saturated hydrocarbons,Those compounds in which the four valencies of carbon atom are not satisfied by single bonds,however satisfied by double or triple bond are called unsaturated hydrocarbons.

Question # 8

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

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 # 10

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.