Soap molecules form micelles in water. The hydrophilic part is: MCQ with Answer and Explanation

Explanation:
Hydrochloric acid (HCl) is commonly used for pickling (cleaning) steel to remove rust and scale (iron oxides) before further processing like galvanizing or plating. Reaction: Fe₂O₃ + 6HCl → 2FeCl₃ + 3H₂O. Sulfuric acid is also used. Nitric acid is an oxidizer and would passivate some metals. Acetic acid is too weak.

Explanation:
NPK fertilizers supply the three primary macronutrients: Nitrogen (N), Phosphorus (P), and Potassium (K). Plants also require trace elements (micronutrients) in very small amounts for proper growth, such as Iron, Manganese, Zinc, Copper, Boron, and Molybdenum. Both statements are factually correct.

Explanation:
Cathode rays are streams of fast-moving electrons, not electromagnetic waves, originating from the cathode in a discharge tube. Because they are material particles traveling in straight lines, they can be stopped by opaque objects, thus casting sharp shadows. Therefore, statements 1 and 3 are correct.