alkanes Flashcards
Define alkanes
A saturated hydrocarbon containing C-H bonds only
What is the general formula of an alkane
CnH2n+2
Are alkane bonds polar? Why?
Non-polar because carbon and hydrogen have similar electronegativities
What is the shape and angle of an alkane?
Tetrahedral
109.5
Describe the sigma bonds in an 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 interactions) becuase 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, so more energy is required to overcome the attraction
Does a branched molecule have a lower or higher boiling point compared to an equivalent straight chain? Why?
The branched molecule has a lower boiling point because they have the 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 a plentiful supply of air
What are the products of complete combustion when alkanes are used?
Carbon dioxide and water
What is incomplete combustion and what products are formed in the case of alkanes?
Combustion in a limited supply of oxygen
Products: water, carbon dioxide and carbon monoxide
