12.1.3 - The ionic product of water Kw

Question 1

What is the Kw of water at 298K?

Answer 1

1*10^-14

Question 2

Why is pure water neutral?

Answer 2

Water dissocates to give an equal number of H+ and OH- ions

Question 3

What happens to strong bases in water?

Answer 3

They completely dissociate

Question 4

If you have the concentration of a strong base, what is this value also equal to?

Answer 4

The concentration of OH- ions

Question 5

Is the dissociation of water exo or endothermic?

Answer 5

Endothermic as heat is required in the form of energy to break bonds down into products

Question 6

What happens to the pH of water as temperature increases?

Answer 6

pH lowers

Question 7

Why does the pH of water decrease at higher temperatures?

Answer 7

Forward reaction of the dissociation of water is endothermic so an increase in pressure favours the production of H+ ions.

Question 8

Why can’t the pH of HCl be diluted to a pH of more than 7?

Answer 8

As the pH approaches 7, the contribution of hydrogen ions from the water is now greater than that of the acid.

Question 9

How much does the pH of a strong acid and a weak acid increase for each 10 fold dilution?

Answer 9

strong acid = increase of 1
Weak acid = increase of 0.5