Which of the following best describes what the pH scale indicates?

• A. The amount of dissolved salts in a solution
• B. The rate of a chemical reaction
• C. The concentration of hydrogen ions (H^+) in a solution
• D. The temperature of a solution

Answer: (C)

Verified step by step guidance

1. Understand that the pH scale is a measure used in chemistry to describe the acidity or basicity of a solution.
2. Recall that pH is defined mathematically 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 a lower pH value indicates a higher concentration of hydrogen ions (more acidic), while a higher pH value indicates a lower concentration of hydrogen ions (more basic or alkaline).
4. Note that the pH scale does not measure the amount of dissolved salts, the rate of chemical reactions, or the temperature of a solution; it specifically relates to hydrogen ion concentration.
5. Conclude that the best description of what the pH scale indicates is the concentration of hydrogen ions (\(\mathrm{H}^+\)) in a solution.