Which of the following is a biofertilizer that fixes atmospheric nitrogen in symbiotic association with legumes?
A. Azospirillum
B. Azotobacter
C. Pseudomonas
D. Rhizobium
Answer: Option D
Solution (By JKSSB Mock Tests)
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:
Bakelite is a thermosetting phenol-formaldehyde resin with excellent heat resistance and electrical insulation properties, making it suitable for switches, handles, and electrical fittings. Polythene and PVC are thermoplastics that soften on heating. Polystyrene is brittle and not highly heat resistant. Thermosets do not melt upon reheating.
Explanation:
The element with atomic number 13 is Aluminum. Its electronic configuration is 2, 8, 3. Since it has 3 electrons in its outermost shell, it loses these 3 electrons to achieve a stable octet configuration, making its valency 3. It forms Al³⁺ ions in chemical compounds.
Explanation:
Faraday constant (F) = 96485 C/mol, approximately 96500 C/mol. It is the magnitude of electric charge per mole of electrons. Charge on one electron = 1.602 × 10⁻¹⁹ C, multiplied by Avogadro's number gives F. Used in electrolysis calculations: mass deposited = (Q × M)/(n × F).
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