Calculate ΔG^∘ at 72^∘ C for reactions in which (a) ΔH^∘=-136 kJ ; ΔS^∘=+457 J / K (b) ΔH^∘=41

step 1 So the standard free energy can be calculated using the Gibbs -Hemholtz equation. We have delta

Calculate ΔG^∘ at 72^∘ C for reactions in which (a)...

Calculate $\Delta G^{\circ}$ at $72^{\circ} \mathrm{C}$ for reactions in which (a) $\Delta H^{\circ}=-136 \mathrm{~kJ} ; \Delta S^{\circ}=+457 \mathrm{~J} / \mathrm{K}$ (b) $\Delta H^{\circ}=41.5 \mathrm{~kJ} ; \Delta S^{\circ}=-0.288 \mathrm{~kJ} / \mathrm{K}$ (c) $\Delta H^{\circ}=-795 \mathrm{~kJ} ; \Delta S^{\circ}=-861 \mathrm{~J} / \mathrm{K}$

Calculate $\Delta G^{\circ}$ at $72^{\circ} \mathrm{C}$ for reactions in which
(a) $\Delta H^{\circ}=-136 \mathrm{~kJ} ; \Delta S^{\circ}=+457 \mathrm{~J} / \mathrm{K}$
(b) $\Delta H^{\circ}=41.5 \mathrm{~kJ} ; \Delta S^{\circ}=-0.288 \mathrm{~kJ} / \mathrm{K}$
(c) $\Delta H^{\circ}=-795 \mathrm{~kJ} ; \Delta S^{\circ}=-861 \mathrm{~J} / \mathrm{K}$

Key Concepts

Temperature Conversion to Kelvin

Converting temperature from degrees Celsius to Kelvin is essential in thermodynamic calculations because the absolute temperature scale is required in the free energy equation. The conversion is performed by adding 273.15 to the Celsius temperature. This ensures that all temperatures used in the calculation are on the proper absolute scale, which is crucial for accurate computations.

Entropy Change (?S)

Entropy change, denoted as ?S, quantifies the change in disorder or randomness within a system during a process. A positive ?S indicates an increase in randomness, while a negative ?S indicates a decrease. In the context of Gibbs free energy, the T?S term helps assess how the disorder influences the spontaneity of the process, especially under varying temperature conditions.

Enthalpy Change (?H)

Enthalpy change, represented as ?H, refers to the heat absorbed or released by a system during a reaction at constant pressure. It is an important measure of the energy change associated with chemical reactions, where exothermic reactions have negative ?H (release heat) and endothermic reactions have positive ?H (absorb heat). This value is critical in calculating the overall free energy change in a reaction.

Gibbs Free Energy (?G)

Gibbs free energy, denoted as ?G, is a thermodynamic potential that measures the maximum reversible work that may be performed by a thermodynamic system at constant temperature and pressure. It is defined by the equation ?G = ?H - T?S, where ?H is the change in enthalpy, T is the temperature in Kelvin, and ?S is the change in entropy. A negative ?G indicates a spontaneous process under constant conditions.

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