Heavy water (D2O) contains deuterium (an isotope of hydrogen) instead of normal hydrogen. It has a higher molecular mass and absorbs neutrons much less efficiently than ordinary water. Because of this property, it is extensively used as a neutron moderator in certain types of nuclear reactors (like CANDU) to slow down neutrons.
Explanation:
Biofertilizers are living microorganisms that enrich the soil quality. Rhizobium is a symbiotic bacterium found in the root nodules of leguminous plants that fixes atmospheric nitrogen. Urea, NPK, and ammonium sulfate are chemical fertilizers synthesized through industrial processes.
Explanation:
Isobars are atoms of different elements with the same mass number but different atomic numbers. Argon (Z=18) and Calcium (Z=20) both have a mass number of 40, making them isobars. Options A, B, and D are isotopes, as they represent the same element with different mass numbers.
Explanation:
Carbon's ability to form bonds with other carbon atoms (catenation) and its tetravalency (four valence electrons) allow it to form long chains, branches, and rings, leading to millions of organic compounds. The C-C bond is strong (bond energy ~348 kJ/mol). Silicon also shows catenation but to much lesser extent. Carbon also forms multiple bonds, enhancing diversity.
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