M4 ,, Alkanes

Question 1

Alkane shape?

Answer 1

tetrahedral and the bond angle is 109.5

shape is tetrahedral as a result of the four bond pairs of electrons equally repelling.

Question 2

Cracking?

Answer 2

conversion of large hydrocarbons to smaller molecules of by breakage of C-C bonds

High Mr alkanessmaller Mr alkanes+ alkenes + (hydrogen)

Question 3

Economic reasons for cracking?

Answer 3

• The petroleum fractions with shorter C chains (e.g. petrol and naphtha) are in more demand than larger fractions.
• To make use of excess larger hydrocarbons and to supply demand for shorter ones, longer hydrocarbons are cracked.
• The products of cracking are more valuable than the starting materials (e.g. ethene used to make poly(ethene), branched alkanes for motor fuels, etc.)

Question 4

Cracking conditions?

Answer 4

Conditions:
Slight pressure
High Temperature (450°C)
Zeolite Catalyst