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Calculating the PH for Strong Acids
Composed and Designed by Mark H. AP Chem. 04-05!
PH is the calculation, to find out the acidity of a solution. In equations, P stands for the -log of something. So in this case PH is the -log[H+].
Because, we are working with strong acids, which dissociate completely into their ions, the molarity of the solution is equal to the molarity of the H+.
| The 7 Strong Acids |
| HCl |
hydrochloric acid |
| HNO 3 |
nitric acid |
| H 2 SO 4 |
sulfuric acid |
| HBr |
hydrobromic acid |
| HI |
hydroiodic acid |
| HClO4 |
perchloric acid |
So all you have to do is take the Molarity of the Strong Acid Solution, and plug it into the [H+] of the PH= -log[H+].
Example #1
What is the PH of a .023M solution of HCL?
- Because HCl is a strong acid, it dissociates 100%, into H+ and Cl-, so therefore [H+]=.023M.
- PH=-log[H+]
- PH=-log(.023M)
- PH= 1.638
- PH= 1.64
Example #2
What is the PH of a .037M solution of HI?
Click Here For the Work