Plaster of Paris is CaSO₄·½H₂O. It is made by heating gypsum (CaSO₄·2H₂O) at 373 K. It sets with water to form gypsum again. Used for plastering fractured bones, making statues.
Explanation:
CO₂ is a major greenhouse gas that absorbs infrared radiation and re-emits it, warming the atmosphere. Other GHGs: CH₄, N₂O, water vapor, CFCs. N₂ and O₂ are diatomic homonuclear molecules that do not absorb IR and are not GHGs. Hydrogen is not a GHG. The increase in CO₂ due to human activities is driving climate change.
Explanation:
Haber process synthesizes ammonia using iron catalyst. Solvay process for soda ash uses no solid catalyst but involves reactions with CO₂ and ammonia. Bayer's process for alumina uses NaOH, no catalyst. Hall-Héroult process is electrolytic for aluminium. Catalysis is key in many industrial processes: Contact (V₂O₅), Ostwald (Pt), hydrogenation (Ni).
Explanation:
In 2Na + Cl₂ → 2NaCl, sodium is oxidized (Na → Na⁺ + e⁻) and chlorine is reduced (Cl₂ + 2e⁻ → 2Cl⁻). It involves change in oxidation states. Options A and B are double displacement (no change in oxidation states). Option D is decomposition with no change in oxidation states (Ca: +2 remains +2). Redox reactions involve simultaneous oxidation and reduction.
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