Does iodine turn yellow or black when starch is present in a

solution?

Black color

Explanation:

Starch is a form of glucose which is stored by the plants in their cells. The structure of starch contains both linear glucose chain called amylose and branched-chain called amylopectin chains. To test the presence of the starch in the solution the iodine test is performed.

When iodine is added to the starch solution, the triiodide ions complex enters the amylose structure of the starch and make the amylose as charge donor. The neutral iodide ions present in the solution act as charge acceptor and form complex. This complex absorbs the light and imparts blue-black color.

Thus, black color is the correct answer.