12.1 - Properties Of The Alkanes

Question 1

What is the general formula for alkane?

Answer 1

CnH2n+2

Question 2

What is the bond angle around each atom in an alkane? Why?

Answer 2

109.5°
In an alkane each carbon atom is surrounded by four bonded pairs of electron
The four bonded pairs of electrons repel each other equally resulting in a tetrahedral hale around each carbon atom

Question 3

What type of bonds are the C-C and C-H bonds?

Answer 3

Covalent bonds

Sigma bonds

Question 4

How are sigma bonds formed?

Answer 4

Sigma bonds are formed from the overlap of orbitals directly between bonding atoms
Sigma bonds can freely rotate

Question 5

What is the correlation between the length of a straight chain alkane and it’s boiling point?

Answer 5

As the carbon chain length increases, boiling point increases
BECAUSE
there are more electrons and more points of contact between molecules
The strength of the London forces between molecules increases
More energy is needed to break the intermolecular forces

Question 6

What is the correlation between the length of a branched chain alkane and it’s boiling point?

Answer 6

As the branching in isomers of alkanes increases, boiling point decreases
BECAUSE
there are fewer points of contact between the molecules
The strength of the London forces between molecules decreases
Less energy is needed to break the intermolecular forces

Question 7

Are alkanes soluble in water?

Answer 7

No
Alkanes are non polar molecules and do not dissolve in polar solvents like water
However they will mix with non-polar solvents