Which of the following does the pH scale measure?

• A. The concentration of sodium ions (Na^+) in a solution
• B. The concentration of hydrogen ions (H^+) in a solution
• C. The temperature of a solution
• D. The color intensity of a solution

Answer: (B)

Verified step by step guidance

1. Understand that the pH scale is a measure used in chemistry to indicate the acidity or basicity of a solution.
2. Recall that pH is defined as the negative logarithm (base 10) of the hydrogen ion concentration in a solution, expressed as \(\mathrm{pH} = -\log_{10}[\mathrm{H}^+]\).
3. Recognize that the concentration of sodium ions (\(\mathrm{Na}^+\)), temperature, or color intensity are not what the pH scale measures.
4. Conclude that the pH scale specifically measures the concentration of hydrogen ions (\(\mathrm{H}^+\)) in a solution.
5. Therefore, the correct interpretation of the pH scale is that it measures how acidic or basic a solution is by quantifying the \(\mathrm{H}^+\) ion concentration.