State second law of thermodynamics.(b) Define - Nucleotides.(c) Write chemical reaction for conversion of benzene diazonium chloride into benzene.

Answer:

(a) Second law: the total entropy of a system and its surroundings increases in a spontaneous (irreversible) process; ΔS_total = ΔS_sys + ΔS_surr \(\gt\) 0 (it remains constant for a reversible process at equilibrium).

(b) Nucleotides: the monomer units of nucleic acids, each made of a nitrogenous base, a pentose sugar (ribose or deoxyribose) and a phosphate group; i.e. a nucleoside esterified with phosphoric acid at C-5′ of the sugar.

(c) Reduction with hypophosphorous acid:

C₆H₅N₂⁺Cl^– + H₃PO₂ + H₂O → C₆H₆ + N₂↑ + H₃PO₃ + HCl