Iodine is used in the starch test because in presence of starch it
ATurns pink-violet like permanganate
BTurns red-brown like rust
CTurns blue-black
DTurns yellow-green like chlorine water
Answer & Solution
Correct answer: C. Turns blue-black
1. Iodine binds the amylose chains of starch.
2. The bound iodine absorbs visible light differently.
3. The visible result is a deep blue-black colour.
4. So iodine indicates starch by turning blue-black.
_Source: Selina Concise Biology Class 10, Ch on Photosynthesis (Mistral OCR'd PDF), section on starch test_
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