Anatomy and Physiology II Practice Test

Which statement is true regarding pH levels?

1. A solution with a pH of 5 has more hydrogen ions than a solution with a pH of 2.

2. A solution with a pH of 9 is a base.

3. The pH value increases as the number of hydrogen ions increase.

4. Both A and C are true.

The correct answer is: A solution with a pH of 9 is a base.

The correct understanding of pH levels involves recognizing the scale that defines acidity and basicity. A solution with a pH of 9 is indeed considered a base. The pH scale typically ranges from 0 to 14, with values below 7 indicating acidity (higher concentration of hydrogen ions) and values above 7 indicating basicity (lower concentration of hydrogen ions). Therefore, a solution with a pH of 9 has fewer hydrogen ions compared to neutral water (pH 7) and is classified as a basic solution. Regarding the other statements: A solution with a pH of 5 is less acidic than a solution with a pH of 2; a pH of 5 indicates fewer hydrogen ions than a pH of 2 because pH is a logarithmic scale. Additionally, as the pH value increases, the number of hydrogen ions actually decreases, not increases. Therefore, the correct statement focuses on the basic nature of the solution with a pH of 9.