Ch. 11.3: Representing Formulae

Question 1

What are all the different types of formula?

Answer 1

Molecular 
Empirical 
Structural 
Displayed 
Skeletal

Question 2

Describe molecular formula

Answer 2

Shows the number and type of atoms of each element present in a molecule. It doesn’t show how the atoms are joined together and different molecules can have the same molecule formula.

Question 3

Describe empirical formula

Answer 3

It is the simplest whole number ratio of the atoms of each element present in a compound.

Question 4

Describe general formula

Answer 4

This is the simplest algebraic formula for any member of a homologous series.

Question 5

Describe displayed formula

Answer 5

This shows the relative positioning of all the atoms in a molecule and the bonds between them.

Question 6

Describe structural formula

Answer 6

This uses the smallest amount of detail necessary to show the arrangement of the atoms in a molecule. It shows clearly which groups are bonded together.

Question 7

Describe skeletal formula.

Answer 7

It is a simplified organic formula. You remove :

• all the carbon and hydrogen labels from carbon chains
• any bonds to hydrogen atoms

This leaves just a carbon skeleton and any functional groups.
In skeletal formula :
- a line represents a single bond
- an intersection of two lines represents a carbon atom
- the end of a line represents a -CH3 group

Question 8

What is one of the most common uses of skeletal formula?

Answer 8

Representing alicyclic and aromatic compounds e.g. cyclohexane , cyclohexene, and benzene.