Question

Which chemical is used to detect transpiration comparatively?

• A. Calcium carbonate
• B. Cobalt carbonate
• C. Cobalt chloride
• D. Mercuric acetate

Answer 1

The correct option is C Cobalt chloride

• Transpiration is the loss of water in vapour form through stomatal pores. Comparatively more stomata are present on the lower leaf surface than the upper leaf surface.
• Cobalt chloride changes its colour on exposure to water. So, a paper dipped in cobalt chloride can be placed on both the upper and lower surfaces of a leaf as a qualitative test for transpiration.
• The liquid water changes the colour of dry cobalt chloride paper from blue to pink. This is a positive test for water that was given off during transpiration.
• This change will occur rapidly on the lower surface as compared to the upper surface.
• Thus, the correct answer is (C).