Which of the following metals is obtained by the reduction of its oxide by aluminium?
A. Sodium
B. Iron
C. Zinc
D. Manganese
Answer: Option D
Solution (By JKSSB Mock Tests)
Manganese is extracted by the aluminothermic process (Goldschmidt thermite process) where Mn₃O₄ is reduced by aluminium: 3Mn₃O₄ + 8Al → 9Mn + 4Al₂O₃. This works for metals with less reactivity than Al but not too reactive. Sodium is extracted by electrolysis. Iron is extracted by smelting with coke. Zinc by carbon reduction/electrolysis.
Explanation:
Azotobacter is a free-living aerobic bacterium that fixes atmospheric nitrogen in the soil, making it available to non-leguminous crops. Rhizobium is symbiotic and specific to legumes. Nitrobacter and Nitrosomonas are involved in nitrification (converting ammonia to nitrites/nitrates), not nitrogen fixation.
Explanation:
Sulfur forms cross-links between polyisoprene chains, converting sticky raw rubber into strong, elastic material. Process discovered by Goodyear.
Explanation:
Atomic number (Z) is defined as the number of protons in the nucleus of an atom. It determines the identity of the element. In a neutral atom, the number of electrons equals Z. Mass number = protons + neutrons.
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