3.2: Titration of a Strong Acid with a Strong Base

During the titration of a strong acid with a strong base, the pH calculations are based on the concentration of the residual H₃O⁺ or OH⁻ ions.

For instance, 0.1 M HCl dissociates into 0.1 M H₃O⁺ and Cl⁻ ions, starting with an initial pH of approximately 1.

The introduction of 0.1 M NaOH alters the H₃O⁺ concentration in the solution. The new concentration can be calculated by subtracting the total moles of OH⁻ from those of H₃O⁺ and dividing by the total volume. Now, the resultant pH has risen to 1.48.

The continued addition of NaOH solution neutralizes all the H₃O⁺, raising the pH to 7 at the equivalence point.

Beyond this point, OH⁻ govern and determine the pH.

Adding more NaOH solution containing 0.007 moles of OH⁻ results in a final OH⁻ concentration of 0.017 M with the corresponding pOH of 1.77 and pH of 12.23.