Different Types of Formulae

Question 1

what are the two main ways to refer to an organic compound

Answer 1

• with their name

- or formulae

Question 2

what does a displayed formula show

Answer 2

every atom of every bond separately

Question 3

what would be the displayed formula for ethane

Answer 3

H  H
      |    |
H- C - C - H
      |    |
     H  H

Question 4

how is a structural formula created

Answer 4

by grouping all the atoms joined together by a particular carbon atom

Question 5

what does a structural formula show

Answer 5

• how the atoms unambiguously are joined together

- the bonds between small molecules with a single carbon atom

Question 6

what would be the structural formula of butane

Answer 6

• CH3-CH2-CH2-CH3

- or just CH3CH2CH2CH3

Question 7

what is a skeletal formula

Answer 7

a zig-zag line that shows only the bonds between carbon atoms

Question 8

what does every change in direction and ending of a skeletal formula indicate

Answer 8

• that there is a carbon atom

- you can think of it as the line slightly changing course whenever it reaches a carbon atom

Question 9

what else would be shown on a skeletal formula

Answer 9

atoms other than carbon and hydrogen

Question 10

what would be the skeletal formula of butane and why

Answer 10

• /\/
• the beginning is the first carbon atom with CH3
• then it turns at the second carbon atom with CH2
• then turns again at the third with CH2
• then reaches the end with another CH3

Question 11

why cant C3H7Cl be considered a structural formula

Answer 11

• the chlorine atoms would be bonded either in between carbon atoms or on either side of the carbon chain
• this is because chlorine can only form one bond but it cant form it with a hydrogen that is already bonded with carbon
• and C3H7Cl would wrongly indicate this if it was the structural formula

Question 12

what would C3H7Cl be correctly called and why

Answer 12

• the molecular formulae
• because it only shows the number of atoms in each molecule
• not its structure or the order they are bonded in
• it can also represent more than one compound

Question 13

if the molecular formula of a molecule is CH3Cl, could this be used to work out the structural, display and skeletal formulae and why

Answer 13

• yes, because it is very simple
• there is only one way in which those atoms could be arranged
• so that is in effect also its structural formula

Question 14

what is the empirical formula

Answer 14

the lowest possible whole number ratio of the atoms in a compound

Question 15

what is the empirical formula for butane

Answer 15

• its molecular formula is C4H10

- so its empirical is C2H5

Question 16

what would be the structural and skeletal formulae for chloroethane

Answer 16

• CH3-CH2-Cl
• /\
  Cl