Question

Iodine gives blue-black colour with

• A. Protein
• B. Oil
• C. Starch
• D. Sucrose

Answer 1

The correct option is C

Starch

Explantion for the correct Option:

Option(C):Starch

• Iodine gives a blue-black color with starch.
• Starch is a polymer of Amylose and Amylopectin, of which Amylose is responsible for the blue color of the reaction.
• The Iodine test is used for the determination of the presence of starch in a sample.
• Molecular iodine is not soluble in water, so Potassium iodide is added to it which together forms a polyiodide complex that upon addition of Starch turns intense blue-black color.

Explantion for the incorrect Option:

Option(A):Protein

• Protein does not give a blue-black color with Iodine.
• Hence, the given Option is an incorrect one.

Option(B):Oil

• On Reaction with Iodine, oil does not give a blue-black color.
• Hence, the given Option does not coincide with the correct Option.

Option(D):Sucrose

• Sucrose does not give a blue-black color with Iodine.
• Thus, the given Option does not represent the correct Concept for the answer.

Therefore, Iodine gives a blue-black color with Starch.