The allotrope of carbon used in electrodes and as a neutron moderator in nuclear reactors is:
A. Diamond
B. Charcoal
C. Fullerene
D. Graphite
Answer: Option D
Solution (By JKExamLibrary)
Graphite is used in electrodes (due to electrical conductivity) and as a moderator in nuclear reactors (to slow down neutrons). It is chemically stable and can withstand high temperatures. Diamond is an insulator. Fullerene is a nanomaterial. Charcoal is used as adsorbent and fuel. Graphite blocks are used in RBMK reactors (like Chernobyl) and in advanced gas-cooled reactors.
Explanation:
Permanent hardness is caused by dissolved chlorides and sulfates of calcium and magnesium. It cannot be removed by boiling. It is removed by adding washing soda (sodium carbonate, Na2CO3). The carbonate ions react with the soluble calcium and magnesium salts to form insoluble carbonates, which precipitate out.
Explanation:
2NaHCO₃ (heat) → Na₂CO₃ + CO₂ + H₂O. This is used in baking as CO₂ causes dough to rise. The sodium carbonate formed gives a bitter taste if excess soda is used, hence baking powder (with acid) is preferred.
Explanation:
Jacques Charles formulated the law: V ∝ T at constant P. Hence Charles' law. Gay-Lussac's law relates pressure and temperature at constant volume. Boyle's law: pressure-volume at constant temperature. Avogadro's law: volume-moles at same T & P. Charles also was a pioneer in ballooning.
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