Alkanes

Question 1

Economic reasons for cracking?

Answer 1

-The petroleum fractions with shorter C chains (e.g. petrol ) are in more demand than larger fractions.
- The products of cracking are more valuable than the starting materials
- (e.g. ethene used to make poly(ethene)

Question 2

What are the two main types of cracking?

Answer 2

Thermal cracking :
Conditions:
High pressure (7000 kPa)
High temperature (400°C to 900°C)

Catalytic:
Conditions:
Slight or moderate pressure
High temperature (450°C)
Zeolite catalyst

Question 2

Physical properties, polarity?

Answer 2

-C and H have very similar electronegativities so the bonds are non – polar.
-This means that all alkane molecules will also be non – polar.
- The only intermolecular force (IMF) holding the alkanes together will therefore be Van Der
Waals (VDW) forces of attraction.

Question 3

Physical properties, solubility?

Answer 3

Water molecules are held together by hydrogen bonds and these are much stronger that
VDW so the alkanes are not soluble in water.

Question 4

Pollution from combustion (incomplete),
NOx?

Answer 4

Nitrogen oxides, NOx:
N2 + 02 —-> N0 (g)
NO is toxic and can form acidic gas NO2
NO2
is toxic and acidic and forms acid rain

Question 5

Pollution from combustion (incomplete), CO

Answer 5

Carbon dioxide Contributes towards global warming

Question 6

Pollution from combustion (incomplete) S02

Answer 6

Acid rain

Question 7

flue gas desulfurisation (S02)

Answer 7

S02 + Ca0 ——> CaS03
a neutralisation reaction

Question 8

Catalytic converters equations for C0 and N0x

Question 9

Catalytic converters equations for C0 and N0x