Gibbs free energy Knowledge-Based Download PDF

Questions

1. 1.

   Under which condition is the instantaneous Gibbs free energy change of a reaction, $\Delta G$, equal to its standard Gibbs free energy change, $\Delta G^\circ$, at a given temperature?

   • A) When the reaction quotient equals 1 ($Q = 1$)
   • B) When the reaction quotient equals the equilibrium constant ($Q = K$)
   • C) When the standard enthalpy change equals the standard entropy change ($\Delta H^\circ = \Delta S^\circ$)
   • D) When the equilibrium constant of the reaction equals 1 ($K = 1$)
2. 2.

   At constant temperature and pressure, the decrease in Gibbs free energy ($-\Delta G$) during a spontaneous process represents the maximum amount of which quantity?

   • A) thermal energy transferred to the surroundings as heat
   • B) non-expansion work that can be performed by the system
   • C) pressure-volume work accomplished by system expansion
   • D) total internal energy that can be converted into mechanical motion
3. 3.

   At constant temperature and pressure, which expression correctly relates the Gibbs free energy change of a system ($\Delta G$) to the total entropy change of the universe ($\Delta S_{\text{univ}}$)?

   • A) $\Delta G = T\Delta S_{\text{univ}}$
   • B) $\Delta G = -\dfrac{\Delta S_{\text{univ}}}{T}$
   • C) $\Delta G = \dfrac{\Delta S_{\text{univ}}}{T}$
   • D) $\Delta G = -T\Delta S_{\text{univ}}$
4. 4.

   At a given temperature, a chemical reaction reaches equilibrium with an equilibrium constant $K$ that is greater than 1 ($K > 1$). Which of the following must be true regarding the standard Gibbs free energy change ($\Delta G^\circ$) for this reaction?

   • A) $\Delta G^\circ < 0$
   • B) $\Delta G^\circ > 0$
   • C) $\Delta G^\circ = 0$
   • D) $\Delta G^\circ = 1$
5. 5.

   For a chemical reaction with a positive standard enthalpy change ($\Delta H^\circ > 0$) and a positive standard entropy change ($\Delta S^\circ > 0$), under which condition is the reaction thermodynamically spontaneous?

   • A) At all temperatures
   • B) Only at temperatures where $T > \frac{\Delta H^\circ}{\Delta S^\circ}$
   • C) Only at temperatures where $T < \frac{\Delta H^\circ}{\Delta S^\circ}$
   • D) At no temperature, because the reaction is always nonspontaneous