Class 2

Question 1

Define Isomerism

Answer 1

Same molecular formula but different structed formula

Question 2

What is a homologous series?

Answer 2

Family of compounds that have:
• same general formula
• similar chemical properties
• same function group
• gradual increase in physical properties such as melting pt. and boiling pt.

Question 3

Hydrocarbon

Answer 3

Contains hydrogen and carbon only.

Question 4

Coal

Answer 4

Solid fuel
• made from decomposition of plants
• mainly contains sulfur as impurities

Question 5

Natural gas

Answer 5

Gaseous fuel (obviously)
• mainly contains methane
• made from decomposition of marine animals

Question 6

Crude oil/petroleum

Answer 6

Liquid fuel
• mixture of hydrocarbons
• made from decomposition of marine animals

Question 7

How are mixtures of hydrocarbons seperated?

Answer 7

Fractional distillation

Question 8

What are fractions?

Answer 8

Groups of hydrocarbons that have different boiling points

• seperated by fractional distillation

Question 9

Refinery gas

Answer 9

• 1-4 carbon atoms in hydrocarbon

* used as fuel

Question 10

Petrol gasoline

Answer 10

• 4-12 carbon atoms in hydrocarbon

* used as fuel in cars

Question 11

Naphtha

Answer 11

• 7-14 carbon atoms in hydrocarbon

* used to make chemicals

Question 12

Parathin kerosine

Answer 12

• 9-16 carbon atoms in hydrocarbon

* used as a fuel in jet engines and as heating oil

Question 13

Diesel oil

Answer 13

• 15-25 carbon atoms in hydrocarbon

* used as fuel in diesal engines

Question 14

Lubricating oil

Answer 14

• 20-50 carbon atoms in hydrocarbon

* used in waxes and polishes

Question 15

Fuel oil

Answer 15

• 20-70 carbon atoms in hydrocarbon

* used as fuel in ships

Question 16

Residue bitumen

Answer 16

• over 70 carbon atoms in hydrocarbon

* used for road surfacing

Question 17

Define cracking

no ur not on crack

Answer 17

Breaking of heavier fractions into smaller molecules

Question 18

Types of Cracking

Answer 18

• Catalytic Cracking

* Thermal Cracking

Question 19

Cracking takes place in a reactor, what happens in this reactor?

Answer 19

Particles of the catalyst made of:
• slice
• alumina
• zeolite
Are mixed with the hydrocarbon fraction.

Question 20

At what temp. does cracking take place in the reactor?

Answer 20

Around 500°C

Question 21

Cracking Formulas

Answer 21

Alkane ➡️ lower alkane + alkene

Alkane ➡️ alkene + hydrogen

(The condition is that it has to be under a high temp. and with a catalyst for this process to take place)

Question 22

Crack C2H6

Answer 22

ETHANE

Alkane ➡️ Alkene + Hydrogen
C2H6 ➡️ C2H4 + H2

Question 23

Cracking of C6H14

Answer 23

Hexane

Alkane ➡️ Lower alkane + alkene
C6H14 ➡️ C3H6 + C3H8
(Hexane ➡️ Propene + propane)
or

C6H14 ➡️ C4H10 + C2H4
(Hexane ➡️ Butane + Ethene)

Question 24

Physical Properties of Alkanes

Answer 24

• States
C1 to C4 ➡️ gas
C4 to C15 ➡️ liquid
C17 and above ➡️ waxy solid

• Boiling Point increases with increase in carbon atoms.

Question 25

Chemical Properties of Alkanes

Answer 25

* Combustion | * Substitution Reaction

Question 26

General Formula for Combustion

Answer 26

Alkane + Oxygen *complete combustion* ➡️ CO2 +Water Alkane + Oxygen *incomplete combustion* ➡️ Carbon monoxide + water

Question 27

What happens during a substitution reaction?

Answer 27

Hydrogen from the alkanes is replaced by a halogen *chlorine or bromine*

Question 28

What is the condition required for substituition reaction to take place?

Answer 28

Presence of SUNLIGHT 🌄

Question 29

General Formulas for Substituition Reaction

Answer 29

Alkane + Halogen ➡️ Haloalkane + Hydrogen halide Alkane + Chlorine ➡️ Chloroalkane + Hydrogen chloride Alkane + Bromide ➡️ Bromoalkane + Hydrogen bromide

Question 30

Physical properties of Alkenes

Answer 30

•States At room temp. ETHENE, PROPENE, BUTENE = colorless gases PENTENE = liquid • Boiling pt. Gradual increase in b.p. as the molecules become larger.

Question 31

Chemical properties of Alkenes

Answer 31

* more reactive than alkanes (haha loser) * bc double bonds break to form single bonds and add on to other atoms. • undergo combustion & addition reaction

Question 32

Describe combustion in alkenes

Answer 32

Alkenes burn in excess oxygen to form carbondioxide and water. Alkene + Oxygen ➡️ CO2 + Water

Question 33

Describe Addition Reaction in Alkenes

Answer 33

Hydrogen is added to the alkene (HYDROGENATION) Alkene + Hydrogen *prescense of nickel* ➡️ alkane Ex. ETHENE +HYDROGEN ➡️ *prescense of nickel* ETHANE