Free energy is the energy that is available to do work in a system. It is calculated as the difference between the enthalpy and the product of the temperature and entropy of a reaction. In a chemical reaction, the free energy change (ΔG) determines whether the reaction is spontaneous (ΔG < 0) or non-spontaneous (ΔG > 0).
the Gibbs free energy (G) of a system is equal to the enthalpy (H) minus the temperature (T) multiplied by the entropy (S). This equation is used to determine whether a reaction is spontaneous (ΔG < 0) or non-spontaneous (ΔG > 0) at a given temperature.
The enthalpy of formation (deltaHf) is the enthalpy change when 1 mole of a compound is formed from its constituent elements in their standard states. The deltaH of a reaction is the difference in enthalpy between the products and the reactants. The deltaH of a reaction can be calculated by taking the sum of the deltaHf of the products minus the sum of the deltaHf of the reactants.
Enthalpy change is not the only consideration for whether a reaction is favorable. However, if the enthalpy change is large, it is usually the dominant factor in determining favorability. Therefore, reactions that have a large, negative tend to be favorable, because the reaction usually releases energy when it occurs. Reactions that have a large, positive tend to be unfavorable as written, because the reaction usually requires energy to occur.
Spontaneous reactions release free energy. If a reaction is spontaneous, it means that it can occur without outside intervention because the products are at a lower energy state than the reactants, and the excess energy is released as free energy. The change in free energy (ΔG) for a spontaneous reaction is negative.
The relationship between enthalpy (H) and entropy (S) is described by the Gibbs free energy equation, ΔG = ΔH - TΔS, where ΔG is the change in Gibbs free energy, ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy. For a reaction to be spontaneous at higher temperatures but not at lower temperatures, the entropy term (TΔS) must dominate over the enthalpy term (ΔH) in the Gibbs free energy equation. This suggests that the increase in entropy with temperature plays a more significant role in driving the reaction towards spontaneity than the enthalpy change.
The standard enthalpy of formation is the energy change when one mole of a compound is formed from its elements in their standard states. The standard enthalpy of reaction is the energy change for a reaction under standard conditions. The relationship between the two is that the standard enthalpy of reaction is the sum of the standard enthalpies of formation of the products minus the sum of the standard enthalpies of formation of the reactants.
In a chemical reaction, enthalpy, entropy, and free energy are related. Enthalpy is the heat energy exchanged during a reaction, entropy is the measure of disorder or randomness, and free energy is the energy available to do work. The relationship between these three factors is described by the Gibbs free energy equation: G H - TS, where G is the change in free energy, H is the change in enthalpy, S is the change in entropy, and T is the temperature in Kelvin. This equation shows that for a reaction to be spontaneous, the change in free energy must be negative, meaning that the enthalpy change and entropy change must work together in the right direction.
In a chemical reaction, the relationship between Gibbs free energy and enthalpy is described by the equation G H - TS, where G is the change in Gibbs free energy, H is the change in enthalpy, T is the temperature in Kelvin, and S is the change in entropy. This equation shows that the Gibbs free energy change is influenced by both the enthalpy change and the entropy change in a reaction.
Gibbs energy accounts for both enthalpy (heat) and entropy (disorder) in a system. A reaction will be spontaneous if the Gibbs energy change is negative, which occurs when enthalpy is negative (exothermic) and/or entropy is positive (increased disorder). The relationship between Gibbs energy, enthalpy, and entropy is described by the equation ΔG = ΔH - TΔS, where T is temperature in Kelvin.
The enthalpy vs temperature graph shows how enthalpy changes with temperature. It reveals that as temperature increases, enthalpy also tends to increase. This indicates a positive relationship between enthalpy and temperature.
The relationship between exothermic formation reactions and their enthalpy of formation values is that exothermic reactions release heat energy when the compound is formed. This results in a negative enthalpy of formation value (hf) because the reaction is giving off energy.
The difference between the enthalpy of the products and the enthalpy of the reactants in a chemical reaction is known as the change in enthalpy, or H. This value represents the amount of heat energy either absorbed or released during the reaction. If H is positive, the reaction is endothermic and absorbs heat. If H is negative, the reaction is exothermic and releases heat.
S > 0 contributes to spontaneity.
To calculate the enthalpy of a reaction, you need to find the difference between the sum of the enthalpies of the products and the sum of the enthalpies of the reactants. This is known as the enthalpy change (H) of the reaction. The enthalpy change can be determined using Hess's Law or by using standard enthalpy of formation values.
The relationship between the change in Gibbs free energy (G) and the spontaneity of a chemical reaction is that a negative G indicates that the reaction is spontaneous, meaning it can occur without outside intervention. Conversely, a positive G indicates that the reaction is non-spontaneous and requires external energy input to proceed.
Its value does not depend on which reactions are added.