Given the following fast equilibrium (below) proposed for the gas phase reaction between NO and O₂, what is the expression for the equilibrium concentration of the intermediate NO₃?
k₁
NO + O₂ ⇌ NO₃
k₋₁
A. k₁[NO]/k₋₁[O₂]
B. k₋₁[NO][O₂]/k₋₁
C. k₁[NO][O₂]/k₋₁
D. k₁[NO][O₂]
E. k₋₁[NO][O₂]
