Which of the following is true regarding chemical equilibrium?
A reaction is in equilibrium if the reaction Gibbs energy ΔrG is zero.
A reaction is in equilibrium if the standard reaction Gibbs energy ΔrG° is zero.
A reaction is in equilibrium if the reaction enthalpy ΔrH is zero.
A reaction is in equilibrium if the standard reaction entropy ΔrS° is zero.