Consider the reaction: H2 S(g)+SO2(g) ⟶3 S(g)+2 H2 O(l) for which ΔH is -233 kJ and ΔS is -424 J

step 1 For this question, we have a chemical reaction of one mole, dihydrogen sulfide, reacting with su

Consider the reaction: H2 S(g)+SO2(g) ⟶3 S(g)+2 H2 O(l) for...

Consider the reaction: $$\mathrm{H}_{2} \mathrm{S}(g)+\mathrm{SO}_{2}(g) \longrightarrow 3 \mathrm{S}(g)+2 \mathrm{H}_{2} \mathrm{O}(l)$$ for which $\Delta H$ is $-233 \mathrm{kJ}$ and $\Delta S$ is $-424 \mathrm{J} / \mathrm{K}$ . a. Calculate the free energy change for the reaction $(\Delta G)$ at 393 $\mathrm{K} .$ b. Assuming $\Delta H$ and $\Delta S$ do not depend on temperature, at what temperatures is this reaction spontaneous?

Consider the reaction:
$$\mathrm{H}_{2} \mathrm{S}(g)+\mathrm{SO}_{2}(g) \longrightarrow 3 \mathrm{S}(g)+2 \mathrm{H}_{2} \mathrm{O}(l)$$
for which $\Delta H$ is $-233 \mathrm{kJ}$ and $\Delta S$ is $-424 \mathrm{J} / \mathrm{K}$ .
a. Calculate the free energy change for the reaction $(\Delta G)$ at 393 $\mathrm{K} .$
b. Assuming $\Delta H$ and $\Delta S$ do not depend on temperature, at what temperatures is this reaction spontaneous?

Key Concepts

Gibbs Free Energy

Gibbs free energy is a thermodynamic potential that combines enthalpy and entropy to determine the spontaneity of a process at a constant temperature and pressure. The expression ?G = ?H - T?S allows one to predict whether a reaction or process will occur spontaneously, with a negative ?G indicating spontaneous behavior and a positive ?G indicating non-spontaneity.

Enthalpy

Enthalpy (?H) represents the total heat content of a system, reflecting the energy changes during a reaction due to bond breaking and formation. It is a central concept in thermodynamics and helps determine whether a reaction is exothermic (releases heat) or endothermic (absorbs heat), both of which influence the free energy change and thus the reaction’s spontaneity.

Entropy

Entropy (?S) is a measure of the disorder or randomness within a system. In thermodynamic processes, changes in entropy play a crucial role in determining the direction of spontaneous processes. When combined with enthalpy in the Gibbs free energy equation, entropy changes can either enhance or offset the energetic favorability of a reaction, especially since they are scaled by temperature.

Temperature Dependence of Reaction Spontaneity

The temperature dependence of reaction spontaneity is derived from the Gibbs free energy equation, ?G = ?H - T?S. This relationship shows that the free energy change for a reaction can vary with temperature, and there exists a critical temperature at which ?G switches sign. This concept is essential for understanding how reactions can become spontaneous under certain temperature conditions even if they are not spontaneous at others.

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