For a particular reaction, ΔH=-32 kJ and ΔS=-98 J / K. Assume that ΔH and ΔS do not vary with

step 1 For an isothermal process, the change in free energy can be represented as G equals delta H, neg

For a particular reaction, ΔH=-32 kJ and ΔS=-98 J / K....

For a particular reaction, $\Delta H=-32 \mathrm{~kJ}$ and $\Delta S=-98 \mathrm{~J} / \mathrm{K}$. Assume that $\Delta H$ and $\Delta S$ do not vary with temperature. (a) At what temperature will the reaction have $\Delta G=0 ?(\mathbf{b})$ If $T$ is increased from that in part (a), will the reaction be spontaneous or nonspontaneous?

Key Concepts

Gibbs Free Energy

Gibbs Free Energy (?G) is a thermodynamic quantity defined by the equation ?G = ?H - T?S, which determines whether a reaction is spontaneous. A negative value of ?G indicates that the reaction can occur spontaneously under constant temperature and pressure, while a positive value means the reaction is nonspontaneous. A ?G of zero defines the equilibrium point between spontaneity and nonspontaneity.

Enthalpy

Enthalpy (?H) represents the heat content of a system and is a measure of the energy absorbed or released during a reaction at constant pressure. An exothermic reaction, which releases heat, has a negative ?H, which can contribute to the spontaneity of the reaction if it overcomes entropy effects.

Entropy

Entropy (?S) quantifies the level of disorder or randomness within a system. In thermodynamics, an increase in entropy is generally associated with a tendency toward disorder. The ?S term in the Gibbs free energy equation, when multiplied by temperature, indicates the additional energy required to overcome or promote this disorder, thus influencing reaction spontaneity.

Temperature Dependence

Temperature is a critical factor in determining the relative contributions of enthalpy and entropy to the Gibbs free energy. By adjusting the temperature, the T?S term changes, which can shift a reaction from being spontaneous to nonspontaneous or vice versa. The temperature at which ?G equals zero is known as the threshold point for spontaneity.

Reaction Spontaneity

Reaction spontaneity refers to whether a chemical reaction can occur without external intervention. It is determined by the sign of ?G: a negative ?G indicates a spontaneous reaction, while a positive ?G indicates that the reaction is nonspontaneous. Assessing reaction spontaneity helps in predicting the behavior of reactions under different temperature conditions.

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