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:
Zinc blende (ZnS) is first concentrated by froth flotation, then roasted in excess air to convert it to ZnO: 2ZnS + 3O₂ → 2ZnO + 2SO₂. ZnO is then reduced with coke at high temperature (smelting) or dissolved in H₂SO₄ and electrolyzed. Roasting is typical for sulfide ores to remove sulfur as SO₂.
Explanation:
Ammonia (NH₃) is manufactured by the Haber process, which involves the direct combination of nitrogen and hydrogen gases at high pressure (200 atm) and moderate temperature (450°C) in the presence of an iron catalyst. The Contact process is for sulfuric acid, and Ostwald's is for nitric acid.
Explanation:
A molecule is the smallest particle of a compound (or element) that can exist independently and exhibit the compound's chemical properties. For covalent compounds (water, CO₂), the molecule is the discrete particle. For ionic compounds, the term 'formula unit' is used rather than molecule. Atoms are smallest particles of elements. Ions are charged atoms/molecules.
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