For the reaction C₂H₆ (g)→ C₂H₄ (g)+ H₂ (g) ΔH° is +137 kJ/mol and ΔS° is +120 J/K ∙ mol.This reaction is ________.

Question

Quizplus · Accepted Answer

The reaction is spontaneous at high temperatures because the positive ΔH° and positive ΔS° values imply that the system is driven by entropy (i.e. disorder). At high temperatures, the increase in entropy has a greater effect on the spontaneity of the reaction, which overcomes the unfavorable enthalpy change. At low temperatures, the favorable enthalpy change is favored, but the decrease in entropy opposes spontaneity. Therefore, the reaction is nonspontaneous at low temperatures.

For the Reaction C2H6 (G)→ C2H4 (G)+ H2 (G)

For the Reaction C₂H₆ (G)→ C₂H₄ (G)+ H₂ (G)