# Enthalpy change and equilibrium

I don't understand why enthalpy change won't change at an equilibrium?

The reason I ask this is because of this question:

At first I thought the answer is C, but I realised that the amount depends on where the position of equilibrium lies. The correct answer is D, but doesn't enthalpy change (delta H) also depend on where the position of equilibrium lies?

• (C) can be incorrect as amount might refer to mass formed, which won't be the same at all. – Tamoghna Chowdhury Dec 31 '15 at 8:28
• Trick questions. (D) is correct since the equilibrium position is reversed as the reaction itself is reversed, so the enthalpy change is also reversed (by your own logic). – Tamoghna Chowdhury Dec 31 '15 at 8:30

The answer to this question is related to the definition of $\Delta H^0$. It is precisely defined as the enthalpy change between the following two thermodynamic equilibrium states: