Gold metal dissolves in aqua regia, a mixture of concentrated hydrochloric acid and conc...

Gold metal dissolves in aqua regia, a mixture of concentrated hydrochloric acid and concentrated nitric acid.

The standard reduction potentials.

are important in gold chemistry. (a) Use half-reactions to write a balanced equation for the reaction of Au and nitric acid to produce and calculate the standard emf of this reaction. Is this reaction spontaneous? (b) Use half-reactions to write a balanced equation for the reaction of Au and hydrochloric acid to produce and calculate the standard emf of this reaction. Is this reaction spontaneous? (c) Use half-reactions to write a balanced equation for the reaction of Au and aqua regia to produce and NO(g), and calculate the standard emf of this reaction. Is this reaction spontaneous under standard conditions? (d) Use the Nernst equation to explain why aqua regia made from concentrated hydrochloric and nitric acids is able to dissolve gold.