The correct option is (c) 2 and 3 only.
Explanation
The testing of food items for major nutrients such as carbohydrates and proteins requires specific chemical reagents prepared through standard laboratory methods.
- Statement 1 is Incorrect: A dilute solution of iodine is not prepared using copper sulphate. It is prepared by adding a few drops of tincture of iodine to a test tube half-filled with water. This solution is used to test for the presence of starch.
- Statement 2 is Correct: Copper sulphate solution is prepared by dissolving approximately 2 grams of copper sulphate in 100 milliliters of water. This solution is required for the Biuret test used to detect proteins.
- Statement 3 is Correct: Caustic soda (sodium hydroxide) solution is prepared by dissolving approximately 10 grams of caustic soda in 100 milliliters of water. This solution acts as the alkaline medium necessary for the protein test.
Key Takeaway: The detection of starch utilizes a dilute iodine solution, whereas the detection of proteins (Biuret test) requires solutions of copper sulphate and caustic soda.