In the molecule CO, there is a coordinate covalent bond. Which atom donates the electron pair? 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:
Tropospheric ozone is not emitted directly; it forms by photochemical reactions of NOx and VOCs in sunlight. So it's a secondary pollutant. CO, SO₂, and lead are primary pollutants emitted directly from sources. Secondary pollutants include ozone, PAN (peroxyacetyl nitrate), and sulfuric acid mist. Ozone at ground level is harmful.

Explanation:
Cement undergoes hydration reactions: water reacts with cement compounds (C₃S, C₂S, C₃A) to form complex hydrated silicates and aluminates (e.g., C-S-H gel) along with Ca(OH)₂. This process causes setting and hardening, forming a rigid, rock-like mass. It is exothermic. Gypsum controls initial setting. Proper curing is necessary for strength development.