How can you distinguish water and ethanol using cobalt chloride paper?

• A. It turns pink to blue with water, but there will be no change with ethanol.
• B. It turns blue with both
• C. It turns pink with ethanol only
• D. It changes to green with water

Answer: (A)

Cobalt chloride paper acts as a moisture indicator: it is blue when dry and turns pink when it absorbs water. Water hydrates the cobalt chloride, creating the pink complex, so the paper changes color. Ethanol doesn’t hydrate cobalt chloride in the same way, so it does not produce the pink color and the paper stays the same. This makes it a simple test to tell water from ethanol: pink indicates water; no color change indicates ethanol.