In a buffer solution consisting of a weak acid and its salt, the ratio of concentration of salt to acid is increased 10-fold, then the pH of the solution
Correct answer: A. increases by one
- A. increases by one
- B. decreases by one
- C. increases by 10-fold
- D. decreases by 10-fold
Explanation
The pH of a buffer solution consisting of a weak acid and its salt depends on the acid dissociation constant (Ka) of the weak acid and the ratio of the concentration of salt to acid. When the ratio of concentration of salt to acid is increased 10-fold, it affects the pH of the solution. To analyze the pH change, let's consider the Henderson-Hasselbalch equation, which relates the pH of a buffer solution to the pKa of the weak acid and the ratio of salt to acid concentrations: pH = pKa + log([Salt]/[Acid]) Initially, let's assume the concentration of the salt is [Salt] and the concentration of the acid is [Acid]. The ratio of salt to acid concentration is [Salt]/[Acid]. When the ratio of concentration of salt to acid is increased 10-fold, the new ratio becomes 10 * [Salt]/[Acid]. Using this new ratio in the Henderson-Hasselbalch equation, the pH of the solution becomes: pH = pKa + log(10 * [Salt]/[Acid]) = pKa + log(10) + log([Salt]/[Acid]) = pKa + 1 + log([Salt]/[Acid]) Therefore, increasing the ratio of concentration of salt to acid 10-fold will result in an increase of 1 unit in the pH of the buffer solution.
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