Which indicator color change indicates the presence of calcium in water?

The presence of calcium in water can be indicated by a color change in certain chemical tests. Specifically, when using a reagent that reacts with calcium, a blue color in the test medium may shift to black when calcium ions are present. This transformation occurs due to the formation of calcium compounds that alter the visual characteristics of the reagents used in the test.

Understanding the chemistry behind this color change is essential for identifying calcium levels in water samples. Calcium is a common element in various geological formations and could influence hardness in water, making its detection vital for water quality assessments.

The other options, while presenting various color transformations, do not correspond to the identification of calcium. Understanding these differences helps clarify the chemical behavior of calcium and how it interacts with the indicators used in testing.