On the pH scale, when acids are added to an aqueous solution, the pH should:

• A. Become exactly $7$
• B. Decrease
• C. Increase
• D. Remain unchanged because pH is independent of acid concentration

Answer: (B)

Verified step by step guidance

1. Recall that pH is a measure of the hydrogen ion concentration in a solution, defined as \(\mathrm{pH} = -\log[\mathrm{H}^+]\).
2. Understand that acids increase the concentration of hydrogen ions (\(\mathrm{H}^+\)) in an aqueous solution.
3. Since pH is the negative logarithm of the hydrogen ion concentration, increasing \([\mathrm{H}^+]\) will cause the pH value to decrease.
4. Therefore, when acids are added to an aqueous solution, the pH should decrease, indicating the solution becomes more acidic.
5. This means the pH will not become exactly 7 (neutral) nor remain unchanged; it will decrease as acid concentration increases.