Question

CoCl3.6H20 forms pink crystals. When they are heated water is evolved and they turn blue. Explain how you could use cobalt chloride as a test for water??

Answer 1

see whether they are pink, as opposed to blue.
google can provide many helpful discussions.

Answer 2

I found this on Google although it is about CoCl2.
https://chlorine.americanchemistry.com/Science-Center/Chlorine-Compound-of-the-Month-Library/Cobalt-Chloride-Colorful-Moisture-Detector/