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EEJ MAIN Chemistry QUESTION #7136
Question 1
The standard Gibbs free energy for a specific reaction is defined by the equation $\Delta_r G^{\circ} = A - BT$, where $A$ and $B$ are non-zero constants. Which statement regarding the thermal nature of the reaction is correct?
  • The reaction is Endothermic if $A > 0$✔️
  • The reaction is Exothermic if $A > 0$ and $B < 0$
  • The reaction is Endothermic if $A < 0$ and $B > 0$
  • The reaction is Exothermic if $B < 0$
Correct Answer Explanation
Comparing $\Delta_r G^{\circ} = A - BT$ with the standard Gibbs-Helmholtz equation $\Delta G^{\circ} = \Delta H^{\circ} - T\Delta S^{\circ}$, we can identify that $A$ represents $\Delta H^{\circ}$ and $B$ represents $\Delta S^{\circ}$. If $A > 0$, then $\Delta H^{\circ} > 0$, which defines an endothermic reaction.