Which of the following is used to chemically test starch?  

The correct answer is lodine solution.Key Points

• Iodine solution is used to chemically test for the presence of starch.
• When iodine solution is added to a sample that contains starch, the solution turns blue-black in color.
• Chlorine solution is not used to test for starch.
  • Chlorine is a strong oxidizing agent and can react with starch, but this reaction is not specific to starch and can occur with other organic compounds as well.
• Sulphur solution is also not used to test for starch.
  • Sulphur is not known to react with starch in a way that produces a visible color change.
• Bromine solution is sometimes used to test for starch, but it is less commonly used than iodine solution.
  • When bromine solution is added to a sample that contains starch, the solution turns orange in color.

Additional Information

• Starch is a complex carbohydrate that is commonly found in plants.
• It is an important source of energy for humans and animals.
• Starch is made up of two types of molecules: amylose and amylopectin.
• Amylose is a linear molecule, while amylopectin is highly branched.
• Both types of molecules can be detected with iodine solution.
• Hence, the correct answer is option 2 (iodine solution) as it specifically reacts with starch to produce a blue-black color.