For each reaction, calculate ΔH°_rxn, ΔS°_rxn

Question

For each reaction, calculate ΔH°_rxn, ΔS°_rxn, and ΔG°_rxn at 25 °C and state whether or not the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous? If so, should the temperature be raised or lowered from 25 °C? d. 2 KClO₃(s) → 2 KCl(s) + 3 O₂(g)

Accepted Answer

Identify the standard enthalpy change ($ \Delta H^\circ $) for the reaction by using standard enthalpies of formation ($ \Delta H_f^\circ $) for each compound involved. Use the formula: $ \Delta H^\circ_{\text{rxn}} = \sum \Delta H_f^\circ (\text{products}) - \sum \Delta H_f^\circ (\text{reactants}) $.. Determine the standard entropy change ($ \Delta S^\circ $) for the reaction using standard molar entropies ($ S^\circ $) for each compound. Use the formula: $ \Delta S^\circ_{\text{rxn}} = \sum S^\circ (\text{products}) - \sum S^\circ (\text{reactants}) $.. Calculate the standard Gibbs free energy change ($ \Delta G^\circ $) for the reaction at 25 °C using the equation: $ \Delta G^\circ_{\text{rxn}} = \Delta H^\circ_{\text{rxn}} - T \Delta S^\circ_{\text{rxn}} $, where $ T $ is the temperature in Kelvin (298 K).. Assess the spontaneity of the reaction by examining the sign of $ \Delta G^\circ_{\text{rxn}} $. If $ \Delta G^\circ_{\text{rxn}} < 0 $, the reaction is spontaneous at 25 °C. If $ \Delta G^\circ_{\text{rxn}} > 0 $, the reaction is non-spontaneous at 25 °C.. If the reaction is non-spontaneous, consider how temperature affects spontaneity. If $ \Delta H^\circ > 0 $ and $ \Delta S^\circ > 0 $, increasing temperature may make the reaction spontaneous. If $ \Delta H^\circ < 0 $ and $ \Delta S^\circ < 0 $, decreasing temperature may make the reaction spontaneous.

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Key Concepts

Thermodynamic Functions (ΔH, ΔS, ΔG)

Spontaneity of Reactions

Temperature's Effect on Spontaneity