Which of the following statements about the pH scale is not true?

A. In a pH expression, the hydronium ions, H3O+, can be abbreviated simply as H+.
B. A solution with a pH of 4 has twice the [H+] of a solution with a pH of 2.
C. The pH scale is based on a scale involving powers of 10.
D. pH is a scale that indicates the acidity of a solution.

B is not true. All of the others are ok

Well, pH is like a balancing act for acids and bases. Now, looking at the options, I'd say that statement A is not true. See, in a pH expression, the hydronium ions, H3O+, are actually represented by more than just H+. It's like they have a little crew with them! So, option A is the odd one out here.

The statement that is not true about the pH scale is:

B. A solution with a pH of 4 has twice the [H+] of a solution with a pH of 2.

To determine which statement about the pH scale is not true, let's go through each statement one by one.

Statement A: "In a pH expression, the hydronium ions, H3O+, can be abbreviated simply as H+."
This statement is true. In a typical pH expression, the concentration of hydronium ions (H3O+) is used as a measure of acidity. For simplicity, the hydronium ions (H3O+) are often abbreviated as H+.

Statement B: "A solution with a pH of 4 has twice the [H+] of a solution with a pH of 2."
This statement is not true. The pH scale is logarithmic, not linear. Each one-unit change in pH corresponds to a ten-fold change in the concentration of hydronium ions (H3O+). Therefore, a solution with a pH of 4 actually has ten times less hydronium ions (H3O+) concentration compared to a solution with a pH of 2, not twice as much.

Statement C: "The pH scale is based on a scale involving powers of 10."
This statement is true. The pH scale is a logarithmic scale based on powers of 10. Each unit change in pH represents a ten-fold change in the concentration of hydronium ions (H3O+).

Statement D: "pH is a scale that indicates the acidity of a solution."
This statement is true. The pH scale is used to measure and indicate the acidity or alkalinity of a solution. A lower pH value indicates higher acidity, while a higher pH value indicates higher alkalinity.

In summary, the statement that is not true is Statement B, which states that a solution with a pH of 4 has twice the [H+] of a solution with a pH of 2.