The main raw material for the manufacture of cement is:
A. Limestone and gypsum
B. Limestone and clay
C. Sand and clay
D. Gypsum and sand
Answer: Option B
Solution (By JKExamLibrary)
Portland cement is primarily made by heating a mixture of limestone (calcium carbonate) and clay (aluminosilicates) in a kiln at about 1450°C to form clinker. A small amount of gypsum is then added to the clinker to control the setting time, but limestone and clay are the main raw materials.
Explanation:
In reaction C, H₂O₂ oxidizes PbS (black) to PbSO₄ (white), where oxygen atoms from H₂O₂ are added. H₂O₂ itself is reduced to H₂O. In reaction D, H₂O₂ oxidizes I⁻ to I₂; that is also oxidation. But the most straightforward oxidizing reaction among these is the restoration of old paintings (PbS → PbSO₄). Reaction A: H₂O₂ reduces O₃ (acts as reducing agent). Reaction B: H₂O₂ reduces Ag₂O. H₂O₂ can act as both oxidizing and reducing agent.
Explanation:
Acid rain results from SO₂ and NOₓ (oxides of nitrogen) dissolving in water vapor to form sulfuric and nitric acids. These are released from burning fossil fuels and industrial processes. Carbon dioxide forms weak carbonic acid (normal rain pH ~5.6), but SO₂ and NOₓ cause pH below 5.0.
Explanation:
Two or more substances (SO₂ and O₂) combine to form a single product (SO₃). This is a combination reaction. It is also a redox reaction and is catalyzed by V₂O₅ in the Contact process for sulfuric acid. Decomposition is the opposite (breaking down). Displacement involves replacement of an element.
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