Cement is mixed with water, it sets into a hard mass due to:
A. Reduction
B. Hydration
C. Evaporation
D. Oxidation
Answer: Option B
Solution (By JKSSB Mock Tests)
Cement compounds react with water (hydration) forming hydrated silicates and aluminates, which crystallize and interlock, giving strength. This is exothermic.
Explanation:
Nickel (finely divided) is used as a catalyst in the hydrogenation of unsaturated vegetable oils to saturated fats (vanaspati ghee). The reaction adds H₂ across double bonds. Platinum and palladium are also hydrogenation catalysts but nickel is cheaper and industrially preferred. Fe is used in Haber process for ammonia synthesis, V₂O₅ in contact process for H₂SO₄. Catalysts provide an alternative pathway with lower activation energy.
Explanation:
Graphite slows down fast neutrons in nuclear reactors, enabling sustained chain reaction. Diamond is hard and insulating; fullerenes are nanomaterials; charcoal is adsorbent.
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