The discovery of the electron was done by: 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:
Vitamins are classified into fat-soluble (A, D, E, K) and water-soluble (B-complex and C) groups. Vitamin C (ascorbic acid) is water-soluble, meaning it dissolves in water and is not stored in the body to a significant extent, requiring regular dietary intake. Vitamins A, D, and K are fat-soluble.

Explanation:
Smelting involves heating a metal oxide ore (roasted or calcined) with a reducing agent like coke (carbon) or CO to obtain the metal in the molten state. Example: Fe₂O₃ + 3CO → 2Fe + 3CO₂ in blast furnace. Calcination: heating carbonate/ hydroxide ore in absence of air. Roasting: heating sulfide ore in excess air. Leaching: chemical dissolution of ore. Smelting is a key pyrometallurgical step.