12.1 Properties of Alkanes

Question 1

What are alkanes?

Answer 1

The main components of natural gas and crude oil

Question 2

What is the general formula of alkanes?

Answer 2

CnH2n+2

Question 3

Are alkanes saturated or unsaturated?

Answer 3

Saturated, they only have single bonds

Question 4

What type of bond joins carbon atoms to other other atoms?

Answer 4

Sigma bond

Question 5

What is a sigma bond a result of?

Answer 5

The overlap of two orbitals, one from each bonding atom

Question 6

How many electrons does each overlapping orbital contain?

Answer 6

one

Question 7

What type of arrangement is around each carbon atom?

Answer 7

A tetrahedral arrangement, 109.5 degrees

Question 8

How many sigma bonds does each carbon atom have?

Answer 8

four

Question 9

What is the pattern of boiling point in alkanes?

Answer 9

As the chain length of alkanes increases, the boiling point also increases.

Question 10

Why does the bpt. of alkanes increase as the chain length gets longer?

Answer 10

There are more electrons and more points of contact therefore london forces are stronger and occur more often.

Question 11

What has a lower bpt. straight chain alkanes or branched alkanes?

Answer 11

Branched alkanes

Question 12

Why do branched alkanes have a lower bpt.?

Answer 12

There are fewer surface points of contact between molecules of branched alkanes, giving fewer london forces.
Branches can not get as close together as straight chain molecules, decreasing the intermolecular forces further.