Question

Water vapour evaporates from leaves. This process is called transpiration. This may be investigated by placing a plastic bag over the shoot of a plant as shown. Drops of a liquid appear on the inside of the bag. Cobalt chloride paper will be changed into ___________ colour if the drops of liquid are drops of water.

• A. The liquid changes the colour of cobalt chloride paper to pink
• B. The liquid changes the colour of cobalt chloride paper to blue
• C. The liquid changes the colour of cobalt chloride paper to white
• D. The liquid changes the colour of cobalt chloride paper to black

Answer 1

The correct option is A

The liquid changes the colour of cobalt chloride paper to pink

Cobalt chloride paper will be changed into pink colour if the drops of liquid are drops of water. Cobalt chloride is a compound that changes colour in response to humidity. As humidity increases, cobalt chloride changes color from sky blue to pink. Such striking changes in color make cobalt chloride useful as a humidity indicator in weather instruments.