Water

Question 1

What is the concentration of hydrogen (H+) ions in water?

Answer 1

the concentration of hydrogen ions in water is 1x10^-7

Question 2

What is the concentration of OH- ions in water?

Answer 2

1x10^-7

Question 3

What is the equation for pH?

Answer 3

pH= -log[H+]

Question 4

Define the heat of vapourisation

Answer 4

Energy required to convert 1g of water from liquid to gas at 25°C

Question 5

What is the pH of water?

Answer 5

pH7

Question 6

Describe the bonding in a water molecule

Answer 6

In a water molecule, a covalent bond forms as the two hydrogen atoms share an electron with the oxygen. These additional two electrons allow oxygen to fill its 2p orbitals making it more stable. The covalent bonds in water are single and polar. Because oxygen is more electronegative than hydrogen, the region around oxygen has a partial negative charge and the region near the two hydrogen atoms has a partial positive charge allowing the formation of hydrogen bonds with other polar molecules.

Question 7

Describe the shape of water molecules

Answer 7

In water, each atom is directed towards the corners of a tetrahedron but with the two lone pairs of electrons on the oxygen, the bond angle is reduced. This is because lone pairs of electrons repel more than bonds (giving a bent structure)

Question 8

What properties of water can be attributed to hydrogen bonding?

Answer 8

• High boiling point (compared to molecules with similar mw)
  
  • Higher cohesion/ adhesion
  • High heat of vaporisation (Energy to convert 1g of water from liquid to gas at 25°C)
  • Ice has a more open structure than water so floats
  • Higher surface tension
  • Higher specific heat capacity
    Oil drop effect