【Daily Question】Theoretical Foundation 2020.08.18
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Multiple-choice question: Given the reaction N2(g) + 3H2(g) → 2NH3(g), △rHm
The enthalpy change () refers to the amount of energy change that occurs when a chemical reaction takes place between substances, while the entropy change () refers to the change in the degree of disorder of an object after a chemical or physical change occurs. At low temperatures, chemical reactions occur spontaneously at that time. As the temperature increases, entropy will determine the spontaneity of the reaction. Spontaneous physical and chemical processes in nature generally proceed in the direction of increasing disorder. The parameter that determines the spontaneity of a chemical reaction is the Gibbs free energy ΔG = ΔH – TΔS; when ΔG < 0, the reaction proceeds spontaneously in the forward direction ； When ΔG=0, the reaction is at equilibrium ； When ΔG > 0, the reaction proceeds spontaneously in the reverse direction. Considering the effects of ΔH and ΔS, there are the following 4 cases: ① If ΔH＜0 and ΔS＞0, then ΔG＜0, and the reaction proceeds spontaneously in the forward direction at any temperature ； ②If ΔH＞0 and ΔS＜0, then ΔG＞0, and the reaction is non-spontaneous in the forward direction at any temperature ；
The enthalpy change () refers to the amount of energy change that occurs when a chemical reaction takes place between substances, while the entropy change () refers to the change in the degree of disorder of an object after a chemical or physical change occurs. At low temperatures, chemical reactions occur spontaneously at that time. As the temperature increases, entropy will determine the spontaneity of the reaction. Spontaneous physical and chemical processes in nature generally proceed in the direction of increasing disorder. The parameter that determines the spontaneity of a chemical reaction is the Gibbs free energy ΔG = ΔH – TΔS; when ΔG < 0, the reaction proceeds spontaneously in the forward direction ； When ΔG=0, the reaction is at equilibrium ； When ΔG > 0, the reaction proceeds spontaneously in the reverse direction. Considering the effects of ΔH and ΔS, there are the following 4 cases: ① If ΔH＜0 and ΔS＞0, then ΔG＜0, and the reaction proceeds spontaneously in the forward direction at any temperature ； ②If ΔH＞0 and ΔS＜0, then ΔG＞0, and the reaction is non-spontaneous in the forward direction at any temperature ；