Chapter 12- Alkanes

Question 1

Define an alkane

Answer 1

A saturated hydrocarbon containing only carbon and hydrogen atoms joined together by single covalent bonds

Question 2

What is a sigma bond?

Answer 2

The result of the overlap of two orbitals, one from each bonding atom

Question 3

What is the shape of an alkane ?

Answer 3

Tetrahedral with a bond angle of 109.5 due to repulsion by the four electron pairs around the carbon atom

Question 4

Why does the boiling points of alkanes increase as their chain length increases?

Answer 4

As chain length increases the molecules have a larger surface area so more surface contact possible=greater London forces = more energy required to overcome these forces

Question 5

Why do Branched isomers have lower boiling points that straight chain isomers?

Answer 5

Less points of surface contact between molecules of branched allayed giving fewer London forces and the branches get in the way of the branched molecules getting as close together as straight chain molecules = decrease in London forces further