Chapter 18, Problem 154CP

When copper reacts with nitric acid, a mixture of NO(g) and NO₂(g) is evolved. The volume ratio of the two product gases depends on the concentration of the nitric acid according to the equilibrium

$2{\text{H}}^{+}\left(aq\right)+2{\text{NO}}_{\text{3}}{}^{-}\left(aq\right)+\text{NO}\left(g\right)\rightleftharpoons 3{\text{NO}}_{\text{2}}\left(g\right)+{\text{H}}_{\text{2}}\text{O}\left(l\right)$

Consider the following standard reduction potentials at 25°C:

a. Calculate the equilibrium constant for the above reaction.

b. What concentration of nitric acid will produce a NO and NO₂ mixture with only 0.20% NO₂ (by moles) at 25°C and 1.00 atm? Assume that no other gases are present and that the change in acid concentration can be neglected.