There are two types of acidity: phenolphthalein acidity, which is prevalent ___________, and mineral acid acidity, which tends to be in the ________.

• A. below pH 4.3, lower pH ranges
• B. above pH 4.3, lower pH ranges
• C. below pH 8.3, range of pH 4.3-8.3
• D. above pH 8.3, range of pH 4.3-8.3

Answer: (B)

In water analysis, acidity is described by two components defined by titration endpoints. Mineral acidity corresponds to the portion neutralized up to a very low pH, around 4.3, and is dominated by strong mineral acids—hence it sits in the lower pH ranges. Phenolphthalein acidity refers to the portion that remains to be neutralized as you raise the pH beyond about 4.3 up to around 8.3, so it becomes the dominant acidity in the higher, but not extreme, pH range. Because mineral acidity lies at the lower pH end and phenolphthalein acidity becomes relevant after passing pH 4.3, the statement that phenolphthalein acidity is prevalent above pH 4.3 and mineral acidity is in the lower pH ranges best fits the concept.