Sodium salt of which acid will be needed for the preparation of propane? Write chemical equation for the reaction.

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?

Assign reasons for the following:
(i) Boiling points of n-alkanes increase regularly with the increase in the number of carbon atoms.

(ii) Branched-chain alkanes have lesser boiling points than the straight chain alkanes.

What effect does branching of an alkane chain has on its boiling point ?

Assign reasons for the following:
(i) All C-H bonds in methane are equivalent. 
(ii) Alkanes are called paraffins.

Alkanes with even carbon atoms have higher melting points than alkanes with an odd number of carbon atoms.Explain.

Describe substitution reaction with special reference to halogenation of alkane.

Why does the iodination of methane require an oxidising agent while so much reagent is needed in the chlorination and bromination of methane?