Alkanes Flashcards
What is an alkane?
A saturated hydrocarbon containing C-H bonds only.
What is the general formula of the alkane?
CnH2n+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 degrees
Describe the σ-bond in alkanes.
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 force — induced dipole-dipole interaction, because the bonds are nonpolar
What happens to the boiling point as alkane chain length increases? Why?
The boiling point increases because there is more surface area and so increased 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 and hence less induced dipole-dipole interactions.
Are alkanes soluble in water? Why?
Insoluble because hydrogen bonds in water are stronger than alkanes’ 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
