The dimerization equilibrium of nitrogen dioxide is represented by
N₂O₄(g) ⇌ 2 NO₂(g) ΔH° = +57 kJ mol⁻¹ (for the forward direction)
(a) Determine the sign of ΔS° for the forward reaction at 298 K and justify your answer quantitatively or qualitatively.
(b) Using thermodynamic reasoning, predict how the equilibrium constant K changes with increasing temperature. Explain your reasoning in terms of both ΔH° and ΔS°.
(c) At a particular temperature T₁ the mixture contains 0.020 mol of N₂O₄(g) and 0.040 mol of NO₂(g) in a rigid 1.0-L container. Without performing numerical calculations, predict the direction in which the reaction will spontaneously proceed as the temperature is raised to a higher value T₂ while pressure is kept constant. Justify your prediction.
(d) Industrial chemists wish to shift the equilibrium toward greater formation of NO₂(g) without raising the temperature above 350 K. Propose a modification to the reaction conditions (excluding temperature change) that exploits entropy considerations, and justify how it achieves the desired shift.
(a) Determination and justification of the sign of ΔS°
(b) Prediction and explanation of how K changes with temperature
(c) Prediction of the spontaneous reaction direction upon heating with justification
(d) Entropy-based proposal to shift equilibrium toward NO₂(g) at ≤350 K with justification