A buffer solution contains 0.240 M ammonium chloride and 0.499 M ammonia. If 0.0565 moles of perchloric acid are added to 250 mL of this buffer, what is the pH of the resulting solution? (Assume that the volume does not change upon adding perchloric acid.)

The pH of the resulting solution is 9.02.

Explanation:

The initial pH of the buffer solution can be found using the Henderson-Hasselbalch equation:

Now, the perchloric acid added will react with ammonia:

Also, the moles of ammonium chloride will increase in the same quantity according to the following reaction:

NH₃ + H₃O⁺ ⇄ NH₄⁺ + H₂O    

Finally, we can calculate the pH of the resulting solution:

Therefore, the pH of the resulting solution is 9.02.

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