Which of the following is the purest form of water? MCQ with Answer and Explanation

Explanation:
Chromium (minimum 10.5%) forms a thin, adherent, transparent oxide layer (Cr₂O₃) on the surface, preventing further oxidation. Nickel adds ductility and enhances corrosion resistance. Iron is the base; carbon is for hardness but not corrosion resistance.

Explanation:
Ionic character increases with the difference in electronegativity between bonding atoms. In hydrogen halides, electronegativity decreases from F to I (F: 4.0, Cl: 3.0, Br: 2.8, I: 2.5). Thus HF has the largest electronegativity difference (1.9) and highest ionic character. The trend: HF > HCl > HBr > HI. However, HF is still a covalent polar molecule. Exam tip: Electronegativity difference > 1.7 usually indicates ionic bond.

Explanation:
Ostwald process: Catalytic oxidation of NH₃ with air over a platinum-rhodium gauze catalyst at ~800°C to form NO, then NO₂, finally absorbed in water to give HNO₃. Fe is Haber catalyst for NH₃. V₂O₅ is for SO₂ oxidation. Ni for hydrogenation. Pt-Rh alloy gauze provides high surface area and mechanical strength, reducing cost. Nitric acid is used in fertilizers (ammonium nitrate), explosives, and nitration.