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 2H+(aq) + 2NO3–(aq) + NO(g) ⇌ 3NO2(g) + H2O(l) Consider the following standard reduction potentials at 25oC:
3e- + 4H+(aq) + NO3–(aq) → NO(g) + 2H2O(l) ϐo = 0.957 V
e- + 2H+(aq) + NO3–(aq) → NO2(g) + H2O(l) ϐo = 0.775 V
a. Calculate the equilibrium constant for this reaction.
b. What concentration of nitric acid will produce an NO and NO2 mixture with only 0.20% NO2 (by moles) at 25oC and 1.00 atm?
Assume that no other gases are present and that the change in acid concentration can be neglected.