organic chemistry - introduction

Question 1

what is a hydrocarbon

Answer 1

A molecule containing only hydrogen and carbon

Question 2

what is molecular formula

Answer 2

The molecular formula shows the actual number of atoms of each element in a molecule

e.g. butane is C4H10

Question 3

what is general formula

Answer 3

The general formula shows the relationship between the number of atoms of one element to another within a molecule. Members of a homologous series share the same general formula. The general formula for alkanes is CnH2n+2 and the general formula for alkenes is CnH2n.

e.g. butane is CnH2n+2

Question 4

what is structural formula

Answer 4

A structural formula shows how the atoms in a molecule are joined together.

e.g. butane is CH3 - CH2 - CH2 - H3

Question 5

what is displayed formula

Answer 5

The displayed formula is a full structural formula which shows all the bonds in a molecule as individual lines.

e.g. butane

   H    H    H    H H -- C -- C -- C -- C -- H
   H.   H.   H.   H

Question 6

what are isomers

Answer 6

molecules with the same molecular formula but with a different structure

Question 7

what is a functional group

Answer 7

an atom or a group of atoms that determine the chemical properties of a compound.

Question 8

what is a homologous series

Answer 8

a group of substances with:

• the same general formula
• similar chemical properties because they have the same functional group
• a trend (graduation) in physical properties

Question 9

know how many carbon atoms are in molecules based on the start of the name

Answer 9

1 Meth-
2 Eth-
3 Prop-
4 But-
5 Pent-
6 Hex-
7 Hept-
8 Oct-
9 Non-
10 Dec-

Question 10

what is a substitution reaction

Answer 10

where an atom or group of atoms is replaced by a different atom or group of atoms. e.g. when ethane reacts with bromine gas, one of the hydrogen atoms in ethane is substituted by one of the atoms of bromine from within the bromine molecule

CH₃-CH₃ + Br-Br → CH₃-CH₂Br + H-Br

Question 11

what is an addition reaction

Answer 11

An addition reaction occurs when an atom or group of atoms is added to a molecule without taking anything away. e.g. when ethene reacts with bromine gas, the product is simply the addition of the two molecules:

CH₂=CH₂ + Br-Br → CH₂Br-CH₂Br

Question 12

what is a combustion reaction

Answer 12

A combustion reaction is another way to say ‘burning’ and is a reaction with oxygen. Combustion of hydrocarbons with excess oxygen gives the products water and carbon dioxide, and also releases heat energy (exothermic reaction). e.g. the combustion of propane

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O