Consider the reaction NH4^+(a q) ⇌H^+(a q)+NH3(a q) Use ΔGi^∘ for NH3(a q) at 25^∘ C=-26.7 kJ /

step 1 Continuing on with our work relating to thermodynamics, we can first calculate the standard free

Consider the reaction NH4^+(a q) ⇌H^+(a q)+NH3(a q) Use...

Consider the reaction $$\mathrm{NH}_{4}^{+}(a q) \rightleftharpoons \mathrm{H}^{+}(a q)+\mathrm{NH}_{3}(a q)$$ Use $\Delta G_{i}^{\circ}$ for $\mathrm{NH}_{3}(a q)$ at $25^{\circ} \mathrm{C}=-26.7 \mathrm{~kJ} / \mathrm{mol}$ and the appropriate tables to calculate (a) $\Delta G^{\circ}$ at $25^{\circ} \mathrm{C}$ (b) $K_{\mathrm{a}}$ at $25^{\circ} \mathrm{C}$

Consider the reaction
$$\mathrm{NH}_{4}^{+}(a q) \rightleftharpoons \mathrm{H}^{+}(a q)+\mathrm{NH}_{3}(a q)$$
Use $\Delta G_{i}^{\circ}$ for $\mathrm{NH}_{3}(a q)$ at $25^{\circ} \mathrm{C}=-26.7 \mathrm{~kJ} / \mathrm{mol}$ and the appropriate tables to calculate
(a) $\Delta G^{\circ}$ at $25^{\circ} \mathrm{C}$
(b) $K_{\mathrm{a}}$ at $25^{\circ} \mathrm{C}$

Key Concepts

Acid Dissociation Constant (K?)

The acid dissociation constant, K?, quantifies the strength of an acid in solution by measuring the extent of its ionization into its conjugate base and a proton. It is defined as the equilibrium constant for the dissociation reaction of the acid. In thermodynamic terms, K? can also be related to the standard Gibbs free energy change of the dissociation process, providing insight into how readily an acid releases hydrogen ions in solution.

Standard Gibbs Free Energy (?G°)

Standard Gibbs free energy is a thermodynamic quantity that indicates the spontaneity of a reaction under standard conditions. It represents the difference in free energy between products and reactants, and a negative value of ?G° suggests that the reaction can proceed spontaneously. This concept is central to predicting the thermodynamic favorability of reactions in both chemical and biochemical processes.

Relationship Between ?G° and the Equilibrium Constant (K)

There exists a fundamental relationship between the standard Gibbs free energy change and the equilibrium constant of a reaction, expressed by the equation ?G° = -RT ln K, where R is the universal gas constant and T is the absolute temperature. This equation shows that a large negative ?G° corresponds to a large equilibrium constant, indicating that the reaction strongly favors product formation at equilibrium.

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