The chemical formula for pH is
pH = - log10[H+] where [H+] is the hydrogen ion concentration in moles per litre or M
Example: Calculate the pH of a 0.25 M or 0.25 mol L-1 solution.
pH = - log10[H+]
pH = - log10[0.25]
pH = -(-0.60) since log10[0.25] = -0.60
pH = 0.60
Calculate the pH of the following solutions of hydrogen ions. Use the pH calculator provided
| pH = -0.70 5.0 M |
pH = 0.65 0.225 M |
pH = -0.30 2.0 M |
pH = 0.0 1.0 M |
pH = 0.52 0.30 M |
| pH = 0.30 0.50 M |
pH = 1.65 0.0225 M |
pH = 0.70 0.20 M |
pH = 1.0 0.01 M |
pH = 2.52 0.0030 M |
For strong monoprotic acids like hydrochloric acid HCl and nitric acid HNO3 the concentration of the acid is equal to the concentration of H+ ions.
Example: Calculate the pH of a 0.10 M or 0.10 mol L-1 solution of nitric acid.
HNO3(aq) →H+(aq) + NO3-(aq)
0.10M 0.10M 0.10M∴ [H+] = 0.10 M
pH = - log10[H+]
pH = - log10[0.10]
pH = -(-1.0) since log10[0.10] = -1.0
pH = 1.0
However, for diprotic acids like sulfuric acid H2SO4 this is not the case. A diprotic acid produces two moles of hydrogen ions per mole of acid.
Example: Calculate the pH of a 010 M or 0.10 mol L-1 solution of sulfuric acid.
Sulfuric acid is a diprotic acid. When it fully dissociates it produces twice the number of moles of H+ ions.
H2SO4(aq) →2H+(aq) + SO42-(aq)
0.10M 0.20M 0.10M∴ [H+] = 0.20 M which is twice the concentration of H2SO4
pH = - log10[H+]
pH = - log10[0.20]
pH = -(-0.70) since log10[0.20] = -0.70
pH = 0.70
Calculate the pH of the following solutions of strongs acids. Use the pH calculator provided
| pH = -1.0 5.0 M H2SO4 |
pH = 0.19 0.55 M HNO3 |
pH = -0.46 0.350 M HCl |
pH = -0.30 2.0 M HCl |
pH = 0.40 0.20 M H2SO4 |
| pH = 0.22 0.60 M HNO3 |
pH = 1.40 0.0325 M HCl |
pH = -0.04 0.550 M H2SO4 |
pH = 0.0 1.0 M HNO3 |
pH = 2.10 0.0040 M H2SO4 |