Use information from this chapter and previous chapters to write chemical equations to represent the following:

(a) Equilibrium between nitrogen dioxide and dinitrogen tetroxide in the gaseous state; 

(b) The reduction of nitrous acid by N₂H₅⁺ forming hydrazoic acid, followed by the reduction of additional nitrous acid by the hydrazoic acid, yielding nitrogen and dinitrogen monoxide; 

(c) The neutralization of H₃PO₄(aq) to the second equivalence point by NH₃(aq).