Alkanes

Question 1

Trend of BP MP of straight chain alkanes

Answer 1

Increase as number of carbons increase

Question 2

MP BP of branched alkanes compared to straight chain

Answer 2

Lower, due to lower packing efficiency, less SA of contact, lower id-id interactions of molecules

Question 3

Trend of density in alkanes

Answer 3

Increase, as higher Mr -> stronger id-id int. -> molecules closer tgt -> smaller volume

Question 4

Are alkanes soluble in water?

Answer 4

No, only in non-polar solvent

Question 5

Eqn of combustion of alkanes

Answer 5

CxHy + (x + y/4)O2 -> x CO2 + y/2 H2O

Question 6

Elaborate on FRS process

Answer 6

Three steps: Ini, Prop, Termi
Prop is slow step
Ini and Prop involve homolytic fission and formation of free radicals
Termi involves consumption of two radicals to form stable pdt, no radicals regenerated

Question 7

Elaborate on Markovnikov and Zaitsev

Answer 7

Markov: Alkyl groups are weakly e donating, stabilising by shifting their e density towards e deficient carbocation.

Zaitsev: Same principle, in case of elimination, higher substituted product is favoured.

Question 8

Problems on use of petrol

Answer 8

Incomplete combustion, form CO and nitrous oxides. Severe impact on envt, severe enhanced greenhouse effect.

Use of catalytic converter form CO2, O2, N2 via redox and metal catalysts.