Ionic product of water, Kw

Question 1

water self ionises according to the equation:

Answer 1

H2O(l) ⇌ H+(aq) + OH-(aq)

Question 2

applying the self ionisation of water to the equilibrium law gives the expression:

Answer 2

[H+(aq)] [OH-(aq)]
————————- = a constant
[H2O(l)]

Question 3

as [H2O(l)] is constant at a given temperature, we can simplify the equation to:

Answer 3

[H+(aq)] [OH-(aq)] = a constant (Kw)

Question 4

the constant is called………….and given the symbol………….

Answer 4

ionic product of water, Kw

Question 5

a neutral solution is defined as

Answer 5

one in which the hydrogen ion concentration is equal to the hydroxide ion concentration

Question 6

the equation that links pKw and Kw is

Answer 6

pKw = -lg Kw

Question 7

at 298K, when Kw = 1.00 x10-14 mol2 dm-6, pKw =

Answer 7

pKw = 14.00

Question 8

when an acid is dissociated inwater, it produces so many hydrogen ions that the small contribution from the water is insignificant, unless:

Answer 8

the acid concentration is very small

Question 9

sodium hydroxide is a ……………..base

Answer 9

strong

Question 10

NaOH, a strong base, can be considered as……………………..dissociated in dilute solutions

Answer 10

fully

Question 11

a sodium hydroxide solution of concentration 0.1 m dm-3 therefore has a hydroxide ion concentration of

Answer 11

0.1 mol dm-3

Question 12

when temperature increases, the pH of water………………..

Answer 12

decreases

Question 13

when temperature decerases, the pH of water

Answer 13

increases