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pH Calculator

The process by which one calculates the pH of a solution depends up the solution and the process by which the solution was made. There are at least 22 different ways to calculate the pH . . . .

  1. 0.325 M HCl solution (strong acid - 100% ionized)
  2. 10.0 mL of 0.325 M HCl + 4.5 mL H2O (solve as strong acid, but account for the dilution that occurred)
  3. 0.143 M NaOH solution (strong base - 100% ionized)
  4. 10.0 mL of 0.143 M NaOH+ 6.7 mL H2O (solve as strong base, but account for the dilution that occurred)
  5. 0.235 M HF solution (weak acid - HF partially dissociates in water . . . . use the pka)
  6. 10.0 mL of 0.235 M HF + 13.2 mL H2O (solve as weak acid, but account for the dilution that occurred)
  7. 0.543 M NaNO2 solution (weak base - NO2- partially reacts with water . . . . use the pkb)
  8. 10.0 mL of 0.543 M NaNO2 + 11.2 mL H2O (solve as weak base, but account for the dilution that occurred)
  9. HCl + NaOH - acid and base react completely until one (or both) is used up . . . .
    • HCl is in excess (solve as if only a strong acid is present - account for the dilution that occurred)
    • NaOH is in excess (solve as if only a strong base is present - account for the dilution that occurred)
    • equimolar amounts of HCl and NaOH are added (pH = 7)
  10. HCl + HF (the weak acid's ionization is significantly muted - consider only the strong acid's concentration and account for the dilution that occurred)
  11. HCl + NaF - acid and base react completely until one (or both) is used up . . . .
    • HCl is added in excess and HCl / HF are present in the solution (solve as if only a strong acid is present - account for the dilution that occurred)
    • F- is added in excess and F - / HF are present in the solution (solve as a buffer solution using Henderson-Hasselbach Equation)
    • equimolar amounts of HCl and NaF are added and only HF is present in the solution (solve as a weak acid solution - account for the dilution that occurred)
  12. NaOH + NaF (the weak base's reaction with water is significantly muted - consider only the strong base's concentration and account for the dilution that occurred)
  13. NaOH + HF - acid and base react completely until one (or both) is used up . . . .
    • NaOH is added in excess and NaOH / F- are present in the solution (solve as if only a strong base is present - account for the dilution that occurred)
    • HFis added in excess and HF / F -are present in the solution (solve as a buffer solution using Henderson-Hasselbach Equation)
    • equimolar amounts of NaOH and HF are added and only F- is present in the solution (solve as a weak base solution - account for the dilution that occurred)
  14. HF + NaF - this is a buffer solution (solve using Henderson-Hasselback Equation)
  15. HF / F- + HCl - this is a buffer solution to which strong acid is added (react the HCl with the F- and then solve using Henderson-Hasselbach Equation)
  16. HF / F- + NaOH - this is a buffer solution to which strong base is added (react the NaOH with the HF and then solve using Henderson-Hasselbach Equation)

Additionally, the pH change that occurs when an acidic or basic solution is diluted can be determined by the Chem21Labs pH Calculator. The calculator guides students through the many different ways of calculating the pH of a solution and gives students immediate feedback on their calculations. In a pH lab developed by Chem21Labs, the use of this calculator is a required part of the lab . . . . at this time, the pH Calculator is an optional, interactive animation for homework pH problems.