pH and Strong Bases Flashcards
1
Q
what is used to find the pH of strong bases?
A
- the ionisation of water, Kw
2
Q
why is Kw used?
A
- water ionises very slightly, acting as an acid and as a base
3
Q
what is the equation for Kw?
A
`Ka x [H2O(aq)] = [H+(aq)][OH-(aq)]
- Kw = [H+(aq)](OH-(aq)]
- Kw is the ionic product of water
4
Q
is Kw fixed?
A
no, it varies with temperature
5
Q
what is Kw at 298K?
A
1.00 x10-14 mol2dm-6
6
Q
why is Kw important?
A
- the value of Kw at 298K steps up a neutral point in the pH scale
- Kw controls the concentrations of [H+(aq)][OH-(aq)]
7
Q
how can we find the H+ ions concentration?
A
Kw = [H+(aq)][OH-(aq)]
Kw = [H+(aq)] squared
8
Q
At 50 degrees the value of Kw is 5.48 x10-14mol2dm-6. Calculate the pH of pure water at this temperature.
A
pH = 6.63
9
Q
what are the types of bases?
A
- monoacidic base
- diacidic base
10
Q
why is the concentration of water not included in the Kw expression?
A
- the dissociation of water is very small
