Which statement best describes how cobalt chloride paper indicates the presence of water?

• A. Water turns cobalt chloride paper pink.
• B. Water turns cobalt chloride paper green.
• C. Water turns cobalt chloride paper blue.
• D. Water turns cobalt chloride paper yellow.

Answer: (A)

Cobalt chloride paper acts as a humidity indicator because its color changes when it absorbs water. The dry form is blue, and when it takes up water to form the hydrated complex, it turns pink. So the presence of water is indicated by the paper turning pink. Green, blue, or yellow do not reflect the hydrated state of cobalt chloride in this test.