Question

What is iodine solution changing from amber-yellow to blue-black an indication of?

Answer 1

The answer is D. Iodine is used to test for starches and, in the presence of a starch, it will turn a dark blue-black color.

Answer 2

Iodine solution is prepared by dissolving iodine in a solution of potassium iodide. This iodine reagent is amber-yellow colored. When this iodine solution is added to starch solution which is a polysaccharide, the yellow colored reagent changes to blue-block color. This color change is due to the formation of a charge transfer complex between starch and the triioidide present in iodine solution. So, the correct answer is d. the presence of starches or complex carbohydrates