What is the C-O-H bond angle in propan-2-ol and why is this? [4 marks]

The bond angle is 104.5 degrees. This is because of the pairs of electrons around the oxygen atom: it has 2 bonded pairs and 2 lone pairs. Lone pairs and bonded pairs of electrons repel each other. However as lone pairs repel more than bonding pairs this reduces the bond angle between the two bonded pairs to 104.5 degrees.