Assign reasons for the following:
(i) All C-H bonds in methane are equivalent.
(ii) Alkanes are called paraffins.
(i) This is because the carbon atom in methane is sp3 hybridised. Since all orbitals (four) in carbon have equivalent energies and shapes, therefore, they form all equivalent C-H bonds.
(ii) Alkanes are called paraffin because they are little reactive chemically due to the presence of strong and stable C-C bonds, therefore, alkanes take part in chemical reactions only under suitable conditions and are called paraffin.
Alkanes with even carbon atoms have higher melting points than alkanes with an odd number of carbon atoms.Explain.
This is because alkane chains with an even number of the carbon atoms (more symmetrical) pack more closely than those with an odd number of carbon atoms (less symmetrical) in the crystalline state. 
As a result, attractive forces between the individual chains of an alkane with an even number of carbon atoms are greater and thus the melting point is higher.
What happens when:
(i) Propyne is heated with H2 in the presence of nickel at 473 K?
(ii) Water is dropped on aluminium carbide?
(iii) Sodium propionate is heated with sodalime?
(iv) Acetic acid is treated with hydroiodic acid in the presence of red phosphorus at 420 K?
Experiment: Powdered sodium acetate is mixed with four times the amount of soda lime. The mixture is taken in a hard glass tube. It is fitted with the delivery tube.
As the contents of the tube are heated, methane gas is produced. It is collected by the downward displacement of water.
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