What is the pH range for acidic solutions?

Acidic solutions are characterized by a pH value less than 7. This is because the pH scale measures the concentration of hydrogen ions (H⁺) in a solution; as the concentration of H⁺ increases, the pH decreases. In pure water, the pH is exactly 7, which is considered neutral. When the pH drops below 7, it indicates an increase in acidity.

The correct answer identifies the pH range for acidic solutions as 0 to 6.9, which aligns perfectly with the definition of acidity. A solution with a pH of 0 would be highly acidic, while a pH approaching 7 signifies that the solution is becoming less acidic but is still considered acidic until it reaches that neutral point at pH 7. Thus, any pH below 7 indicates an acidic environment.