Balanced net ionic equation for redox reaction

1. Jun 4, 2005

LizziePearl

Just need some idea of where to start on this one....am in my first Chemistry class and it is an intensive so we're not spending a lot of time on things. This one just has me stumped from the beginning so just some guidance on where to begin would be a huge help...

Problem: Gold metal will dissolve only in aqua regia, a mixture of concentraed hydrochloric acid and concentrated nitric acid in 3:1 volume ratio. The products of the reaction between gold and the concentrated acids are AuCL4-(aq), NO(g), and H2O.
a. Write a balanced net ionic equation for the redox reaction, treating HCL and HNO3 as strong acids.
b. What stoichiometric ratio of hydrochloric acid to nitric acid should be used?
c. What volumes of 12 M HCl and 16 M HNO3 are required to furnish the Cl- and NO3- ions to react with 25.0 g of gold?

I started with trying to write the equation given but wasn't sure it was correct because of the statement "3:1 ratio". This is what I started with:
Au+Cl+HNO3 -> AuCl4-+NO+H2O

Then I started trying to do the balanced redox equation by breaking it down but so I started by...
Au -> AuCl4-
HCl -> H2O
HNO3 -> NO

Is this the correct initial approach?

2. Jun 4, 2005

vsage

I don't really like the idea of you treating strong acids as not dissociated on the reactant side of the equation. Remember that $$HNO_3$$ exists as $$H^+$$ and $$NO_3^-$$ in solution, for example. That being said, your half reactions need to be tweaked a little.