4.1.2 Alkanes Flashcards
What is an alkane?
A saturated hydrocarbon containing C-H bonds only
What is the general formula of an alkane?
Cn H2n+2
Are alkane bonds polar?
Why/ why not?
Nonpolar
Because carbon and hydrogen have similar electronegativities
What is the shape and angle of an alkane?
Tetrahedral
109.5
Describe the sigma bond in alkane
The sigma bond is a covalent bond which has a direct overlap of the electron clouds of the bonding atoms
What type of intermolecular forces do alkanes have?
Why?
London forces
Induced dipole-dipole interaction
Because the bonds are non polar
What happens to the boiling point as alkane chain length increases? Why?
The boiling point increases
Because there is more surface area and so more number of induced dipole-dipole interactions. Therefore more energy is required to overcome the attraction
Does a branched molecule have lower or higher boiling point compared to equivalent straight chain? Why?
the branched molecule has a lower boiling point because they have fewer surface area points of contact, so less london forces are present. Less energy is required to overcome this attraction
Are alkanes soluble in water?
Why?
Insoluble because hydrogen bonds in water are stronger than alkane’s london forces of attraction
How reactive are alkanes?
Very unreactive
What reactions will alkanes undergo?
Combustion and reaction with halogens
What type of reaction is combustion?
Oxidation reaction
What is complete combustion?
Combustion that occurs with plentiful supply of air
What are the products of complete combustion when alkanes are used?
Carbon dioxide and water
What is the colour of the bunsen burner flame during complete combustion?
Blue flame
