The Alkanes

Question 1

Define the alkane family of hydrocarbons

Answer 1

A family of hydrocarbons in which all the atoms are linked by single bonds

Question 2

Why are the alkanes said to be a saturated compound?

Answer 2

There are no double or triple bonds present i.e. there is only single bonds

Question 3

Define a saturated compound

Answer 3

A compound in which there are only single bonds between the atoms in the molecule

Question 4

What is a structural formula of a compound?

Answer 4

The structural formula of a compound shows how the atoms of the compound are arranged relative to one another

Question 5

What does each of the alkane compounds end in?

Answer 5

‘ane’

Question 6

Give the names for the first ten alkane compounds

Answer 6

Methane 
Ethane 
Propane 
Butane 
Pentane 
Hexane 
Heptane 
Octane 
Nonane
Decane

Question 7

Give the molecular formulae for the first ten alkane compounds

Answer 7

CH4 
C2H6 
C3H8 
C4H10 
C5H12 
C6H14 
C7H16 
C8H18 
C9H20 
C10H22

Question 8

What form are the first four members of the alkanes in?

Answer 8

They are in the form of gas

Question 9

What form are the next twelve members of the alkanes after the first four in?

Answer 9

Liquid

Question 10

What form are the higher members of the alkanes in?

Answer 10

Waxy solids

Question 11

Why do the boiling points of the alkanes increase with the size of the molecules?

Answer 11

The strength of the van der Waals forces increase

Question 12

Explain how the boiling point of the alkanes increases with the size of the molecule because of the increasing strength of the van der Waals forces
(2)

Answer 12

As the molecules increase in size there is a greater number of electrons in the electron clouds which allow the temporary dipoles to form more easily.

This means more energy is needed to overcome the increasing strength of the van der Waals forces and this causes the increase in boiling points

Question 13

What is the general formula for the alkanes?

Answer 13

CnH2n+2 i.e for every one C there H is double and 2 more are added

Question 14

Define the a homologous series

5

Answer 14

A series of compounds of similar chemical properties

Showing gradations in physical properties

Having a general formula for its members

Each member having a similar method of preparation

Each member differing from the previous member by a (CH2) unit

Question 15

Define structural isomers

Answer 15

Compounds with the same molecular formula but different structural formulas