4.1.6: Properties of alkanes

Question 1

what is bond angle and shape of alkanes?

Answer 1

tetrahedral with bond angle of 109.5°

Question 2

describe the bonding in alkanes

Answer 2

Each of the alkanes covalent bonds has a direct overlap of the electron clouds from each atom making a sigma bond

Question 3

describe the polarity of alkanes

Answer 3

as carbon and hydrogen atoms have similar electronegativity values they are non-polar without any significant dipoles, however as the electrons are always moving there may be a lack of balance causing an instantaneous dipole

Question 4

how does the carbon-chain length affect alkanes boiling point?

Answer 4

as the chain grows longer, the Mr will increase, larger molecules will have more surface area contacts between adjacent molecules increasing number of dipole-dipole forces, requiring more energy for intermolecular attraction to be overcome

Question 5

how does branching affect alkane boiling points?

Answer 5

the more branched a compound is, the fewer surface area interactions there are, therefore less dipole-dipole forces and less energy required to overcome intermolecular attraction