1. pH and concentration

2. HIGHER GRADE CHEMISTRY CALCULATIONS
pH and Concentration
pH is related to the concentration of hydrogen ions.
e.g [H+(aq)] = 1 x 10-1 mol l -1, pH = 1
[H+(aq)] = 1 x 10-6 mol l -1, pH = 6
Also, in aqueous solution, [H+(aq)] x [OH-(aq)] = 1 x mol2 l-2.
Worked example 1.
What is the concentration of OH-(aq) in a solution with a pH of 5?
pH = 5
[H+(aq)] = 1 x mol l-1.
[H+(aq)] [OH-(aq)] = 1 x mol2 l-2.
So [OH-(aq)] = mol l-1.
= 1 x 10-9 mol l-1.
1 x 10-14
1 x 10-5

3. Calculations for you to try.
1. What is the pH of 0.01 mol l-1 hydrochloric acid?
[H+(aq)] = 1 x mol l-1.
pH = 2
2. The concentration of [OH-(aq)] is 1 x mol l-1.
What is the pH of the solution?
[OH-(aq)] = 1 x mol l-1.
H+(aq)] [OH-(aq)] = 1 x mol2 l-2.
So [H+(aq)] = 1 x mol l-1.
pH = 10
3. What is the pH of 0.05 mol l-1 sulphuric acid?
[H+(aq)] = 2 x = mol l-1.
Formula = (H+)2SO42-
[H+(aq)] = 1 x mol l-1.
Higher Grade Chemistry
pH = 1