Chemistry
Grade-7
Easy

Question

Iodine test is used to check the presence of _________.

  1. Fat
  2. protein
  3. Both A and B
  4. Carbohydrates

hintHint:

It is a biomolecule that consists of carbon, hydrogen, and oxygen atoms, usually with a hydrogen-oxygen atom ratio of 2:1.

The correct answer is: Carbohydrates


    • Carbohydrate-containing foods are made of starch, so iodine tests are used to detect carbohydrates. The iodine test is used to check the availability of starch-like carbohydrates in the sample.
    • Starch turns a deep 'blue-black' color upon the addition of an aqueous solution of the triiodide anion due to the formation of intermolecular charge transfer components (complexes).
    • In the iodine-starch test, when the triiodide anion comes into contact with starch, it rapidly turns dark blue-black.
    • Color intensity decreases with increasing temperature and in the presence of water-soluble organic solvents such as ethanol.
    • Starch is hydrolyzed in this state, so the test cannot be performed at a very low pH.

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