Practice question

Given: For the reaction N₂(g) + 2O₂(g) <=> 2NO₂(g), K_c = 0.04 at 500 K. If initial concentrations are [N₂] = 0.2 M and [O₂] = 0.3 M, what is [NO₂] at equilibrium? These values define the system as per NCERT data. Formula: Let [NO₂] = 2x, then [N₂] = 0.2 - x, [O₂] = 0.3 - 2x. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: K_c = frac[NO₂]²[N₂][O₂]² = (2x)²/(0.2 - x)(0.3 - 2x)² = 0.04 . Simplify: 4x² = 0.04 (0.2 - x)(0.3 - 2x)², solve: x approx 0.015, 2x approx 0.03 M. Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.