Why does nitric acid not dissolve gold as well as aqua regia does?

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<a href="http://qanda.encyclopedia.com/question/why-does-nitric-acid-not-dissolve-gold-well-aqua-regia-does-115259.html" >Why does nitric acid not dissolve gold as well as aqua regia does?</a>

Nitric acid is a powerful oxidizing agent (see oxidation and reduction), but the chemical equilibrium for its reaction with gold, Au, only permits formation of a tiny amount of Au +3 ion, so the amount of gold dissolved in pure nitric acid is undetectable. The presence of chloride ion, Cl - , allows formation of the stable chloraurate complex ion , AuCl 4- . Because of the high concentration of chloride ion in aqua regia, the Au +3 is reacted almost as soon as it is formed, keeping its concentration low; this allows oxidation of more Au to Au +3 , and the gold is dissolved.