According to the pH scale, which of the following solutions is considered neutral?

• A. A solution with pH = 2
• B. A solution with pH = 7
• C. A solution with pH = 10
• D. A solution with pH = 5

Answer: (B)

Verified step by step guidance

1. Recall that the pH scale measures the acidity or basicity of a solution, where pH is defined as \(\mathrm{pH} = -\log[\mathrm{H}^+]\), with \([\mathrm{H}^+]\) being the concentration of hydrogen ions.
2. Understand that a neutral solution is one where the concentration of hydrogen ions equals the concentration of hydroxide ions, which occurs at 25°C when \([\mathrm{H}^+] = 1 \times 10^{-7} \; \mathrm{M}\).
3. Recognize that this neutral condition corresponds to a pH value of 7, because \(\mathrm{pH} = -\log(1 \times 10^{-7}) = 7\).
4. Compare the given pH values: pH = 2 (acidic), pH = 5 (acidic), pH = 7 (neutral), and pH = 10 (basic).
5. Conclude that the solution with pH = 7 is considered neutral according to the pH scale.