Which of the following would tell you that a weak base is present? A. An indicator added to the solution turns green-blue.
B. If there is a high reaction rate.
C. If the pH of the solution is close to 14.
D. If the solution is a good conductor of electricity.

A. An indicator added to the solution turns green-blue.

Explanation:

A pH scale measures the concentration of hydrogen ions in acidic and alkaline solutions.

In chemistry, pH literally means the power of hydrogen ions and it is a measure of the molar concentration of hydrogen ions in a particular solution; thus, specifying the acidity, neutrality or basicity of any chemical solution.

Mathematically, the pH of a solution is given by the formula;

On a pH scale, a solution with a pH of 7 is neutral, a solution with a pH below 7 is acidic and it's basic (alkaline) when it's pH is above 7.

A pH indicator can be defined as a compound (substance) that indicates the concentration of hydrogen ions present in a solution by changing its color over a narrow range of pH values.

A pH range of 1 to 3 (1 - 3) represents a strong acid with a red color.

When an indicator added to a solution turns green-blue, it simply means that a weak base is present.