Given the reaction: 2 NO₂(g) ⇌ N₂O₄(g), with equilibrium concentrations [NO₂] = 0.5 M and [N₂O₄] = 0.2 M, calculate the equilibrium constant K.

• A. K = 0.8
• B. K = 0.4
• C. K = 0.8
• D. K = 0.8

Answer: (A)