Homologous Series

Question 1

What is the definition of a homologous series?

Answer 1

A homologous series is a group of hydrocarbons with the same general formula but different chemical properties.

Question 2

What is the general formula of the alkanes?

Answer 2

CnH2n+2

Question 3

What are all the alkanes systematic names up-to eight carbons?

Answer 3

Methane (CH4)
Ethane (C2H6)
Propane (C3H8)
Butane (C4H10)
Pentane (C5H12)
Hexane (C6H14)
Heptane (C7H16)
Octane (C8H18)

Question 4

What is a use of an alkane?

Answer 4

Alkanes such as methane is used for cooking and heating.

Octane is used in petrol for cars.

Question 5

What happens to the MP and BP of homologous series when molecular size increases?

Answer 5

They increase.

Question 6

What is an Alkene?

Answer 6

Alkenes are a family of hydrocarbons containing single and double carbon to carbon bonds.

Question 7

What is the general formula of an alkene?

Answer 7

CnH2n

Question 8

Alkenes are described as “unsaturated”. What is a unsaturated compound?

Answer 8

Compounds containing at least one carbon to carbon double bond are described as unsaturated.

Question 9

What is a cycloalkane?

Answer 9

Cycloalkanes are a family of hydrocarbons containing a ring of single carbon to carbon bonds.

Question 10

What is the general formula of the cycloalkanes?

Answer 10

CnH2n

Question 11

What is an Isomer?

Answer 11

Isomers are molecules with the same molecular formula but a different structural formula.

Question 12

Alkanes and Cycloalkanes are described as “saturated”. What is meant by a saturated compound?

Answer 12

Compounds containing only single carbon to carbon bonds are described as saturated.

Question 13

How can you test if a compound is saturated of unsaturated?

Answer 13

Mix it with bromine solution. If it goes colourless it’s unsaturated and if it stays the same it’s saturated.