6.4 : Hydrogen Bonding

Question 1

Define hydrogen bond

Answer 1

The electrostatic attraction between a lone pair of an electronegative atom and the hydrogen atom of an electronegative atom.

Question 2

List the anomalous properties of water

Answer 2

The solid is less dense than the liquid

It has a relatively high melting / boiling point

Question 3

Explain why ice is less dense than water

Answer 3

Hydrogen bonds hold water molecules apart in an open lattice structure

The water molecules in ice are further apart than in water

Sold ice is less dense than liquid water and floats on

Question 4

How many hydrogen bond can a water molecule form?

Answer 4

Four ( two lone pairs, 2 hydrogen atoms )

Question 5

Explain why water has a relatively high melting point and boiling point

Answer 5

Water has hydrogen bonding over and above the London forces

A greater amount of energy is required to break the hydrogen bonds

Therefore it has a high melting / boiling point