Here are some standard electrode potentials:-

$$SO_4^{2-} + 4H^+ +2e^-\rightarrow SO_2 +2H_2O\\E^o=0.17V\\ NO_3^-+4H^++3e^-\rightarrow NO+2H_2O\\E^o=0.97V\\ NO_3^-+2H^++e^-\rightarrow NO_2+H_2O\\E^o=0.78V$$ When nitric acid reacts with a metal, either nitrogen dioxide or Nitric oxide is formed? How do you predict which is thermodynamically favourable and which will actually take place? For example, when dilute nitric acid reacts with copper, Nitric oxide is liberated and when it is concentrated, Nitrogen dioxide is evolved? As Nitric acid formation is more favourable, shouldn't it proceed in all cases as increasing the concentration will decrease/increase the potential of both the reaction (Nernst equation)?

In case of sulphate ion, although the reduction of sulphate is more favourable than that of hydrogen, it is hydrogen ions getting reduced when a metal reacts at dilute concentrations? why is this so? Moreover, at high concentrations, once again sulphur dioxide is evolved? How can we understand such occurrences? I am comfortable with basic electrochemical equations and those of thermodynamics.

An additional example would be the oxidation of water to yield hydrogen peroxide or oxygen gas. Which pathway would be preferred in different conditions?