Which of the following is a biofertilizer that fixes atmospheric nitrogen in symbiotic association with legumes?
A. Pseudomonas
B. Rhizobium
C. Azospirillum
D. Azotobacter
Answer: Option B
Solution (By JKExamLibrary)
Rhizobium bacteria form root nodules in leguminous plants (peas, beans, clover) and fix atmospheric N₂ into ammonia, providing nitrogen to the plant, while the plant supplies carbohydrates. Azotobacter and Azospirillum are free-living nitrogen fixers. Pseudomonas is a general soil bacterium. Symbiotic association is mutualistic. Inoculating seeds with Rhizobium culture increases soil fertility.
Explanation:
Boyle's law: P ∝ 1/V or PV = constant at constant T and n. So if volume increases, pressure decreases. This is because gas molecules have more space and hit the walls less frequently. An example is a syringe: pulling the plunger increases volume, decreases pressure.
Explanation:
Roasting converts sulfide ores to oxides by heating in excess air: 2ZnS + 3O₂ → 2ZnO + 2SO₂. Calcination is for carbonates; leaching for others.
Explanation:
Water hardness is primarily caused by the presence of dissolved multivalent cations, most commonly calcium (Ca²⁺) and magnesium (Mg²⁺) ions, usually in the form of bicarbonates, chlorides, or sulfates. Sodium and potassium salts do not cause hardness.
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