For each reaction, calculate ΔHrxn^∘, ΔSrxn^∘, and ΔGrxn^∘ at 25^∘ C and state whether or not th

step 1 So today we're calculating delta H, delta S, and Delta G at 25 degrees Celsius for the following

For each reaction, calculate ΔHrxn^∘, ΔSrxn^∘, and ΔGrxn^∘...

For each reaction, calculate $\Delta H_{\mathrm{rxn}}^{\circ}, \Delta S_{\mathrm{rxn}}^{\circ}$, and $\Delta G_{\mathrm{rxn}}^{\circ}$ at $25^{\circ} \mathrm{C}$ 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 $25^{\circ} \mathrm{C} ?$ a. $\mathrm{N}_{2} \mathrm{O}_{4}(g) \longrightarrow 2 \mathrm{NO}_{2}(g)$ b. $\mathrm{NH}_{4} \mathrm{Cl}(s) \longrightarrow \mathrm{HCl}(g)+\mathrm{NH}_{3}(g)$ c. $3 \mathrm{H}_{2}(g)+\mathrm{Fe}_{2} \mathrm{O}_{3}(s) \longrightarrow 2 \mathrm{Fe}(s)+3 \mathrm{H}_{2} \mathrm{O}(g)$ d. $\mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \longrightarrow 2 \mathrm{NH}_{3}(g)$

For each reaction, calculate $\Delta H_{\mathrm{rxn}}^{\circ}, \Delta S_{\mathrm{rxn}}^{\circ}$, and $\Delta G_{\mathrm{rxn}}^{\circ}$ at $25^{\circ} \mathrm{C}$
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 $25^{\circ} \mathrm{C} ?$
a. $\mathrm{N}_{2} \mathrm{O}_{4}(g) \longrightarrow 2 \mathrm{NO}_{2}(g)$
b. $\mathrm{NH}_{4} \mathrm{Cl}(s) \longrightarrow \mathrm{HCl}(g)+\mathrm{NH}_{3}(g)$
c. $3 \mathrm{H}_{2}(g)+\mathrm{Fe}_{2} \mathrm{O}_{3}(s) \longrightarrow 2 \mathrm{Fe}(s)+3 \mathrm{H}_{2} \mathrm{O}(g)$
d. $\mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \longrightarrow 2 \mathrm{NH}_{3}(g)$

Key Concepts

Reaction Enthalpy (?H)

Reaction enthalpy is the measure of the total heat content change during a chemical reaction carried out at constant pressure. It indicates whether the reaction absorbs heat (endothermic, positive ?H) or releases heat (exothermic, negative ?H). This concept is crucial in understanding energy changes in chemical processes, influencing both the reaction rate and the conditions under which a reaction occurs.

Reaction Entropy (?S)

Reaction entropy represents the change in disorder or randomness accompanying a chemical transformation. A positive ?S indicates an increase in system disorder, while a negative ?S reflects a decrease. This change is significant because it, along with enthalpy, helps determine the overall spontaneity of a reaction according to the second law of thermodynamics.

Gibbs Free Energy (?G)

Gibbs free energy is a thermodynamic potential that combines enthalpy, entropy, and temperature to predict whether a reaction will proceed spontaneously. It is calculated using the equation ?G = ?H - T?S. A negative ?G indicates that a reaction is spontaneous under a given set of conditions, making it a central concept in chemical thermodynamics.

Spontaneity of Reactions

The spontaneity of a reaction is determined by the sign and magnitude of its Gibbs free energy change. A reaction with ?G < 0 is considered spontaneous, meaning it proceeds without external input. The interplay between enthalpy and entropy changes, and their dependence on temperature, plays a pivotal role in dictating whether a reaction is self-sustaining under specified conditions.

Temperature Dependence on Reaction Spontaneity

Temperature critically influences the spontaneity of a reaction, as it directly affects the T?S component in the Gibbs free energy equation. When ?H and ?S have the same sign, changes in temperature can shift the balance, potentially rendering a non-spontaneous reaction spontaneous. For instance, raising the temperature makes reactions with a positive ?H and positive ?S more likely to be spontaneous, while lowering temperature favors reactions with a negative ?H and negative ?S.

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