-H, +S
It is not spontaneous.
For a spontaneous reaction, the overall change in enthalpy should be negative (exothermic). This means that the products have a lower enthalpy than the reactants, releasing energy in the form of heat.
It tells if the reaction will process spontaneously or not
At 500K, the reaction rate will increase as temperature rises, following the Arrhenius equation. This increase in temperature will also influence the equilibrium position of the reaction if it is a reversible reaction. Higher temperatures can sometimes shift the equilibrium towards the products or reactants, depending on the enthalpy change.
The reaction will be spontaneous at high temperatures (T) where TΔS > ΔH, according to Gibbs free energy equation, ΔG = ΔH - TΔS. At high enough temperatures, the TΔS term can outweigh the positive ΔH term, leading to a negative ΔG value and a spontaneous reaction.
It is not spontaneous.
The spontaneity of a reaction is determined by the sign of the Gibbs free energy (ΔG). If both enthalpy (H) and entropy (S) are positive, the reaction can be spontaneous at high temperatures where the TΔS term outweighs the positive ΔH term, resulting in a negative ΔG. This means the reaction will be spontaneous at elevated temperatures.
For a spontaneous reaction, the overall change in enthalpy should be negative (exothermic). This means that the products have a lower enthalpy than the reactants, releasing energy in the form of heat.
The reaction is exothermic
It tells if the reaction will process spontaneously or not
A reaction will be spontaneous at low temperatures if the decrease in enthalpy (change in heat content) of the reaction is greater than the decrease in entropy (measure of disorder) multiplied by the temperature. This can be represented by the 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.
The reaction will be spontaneous at high temperatures (T) where TΔS > ΔH, according to Gibbs free energy equation, ΔG = ΔH - TΔS. At high enough temperatures, the TΔS term can outweigh the positive ΔH term, leading to a negative ΔG value and a spontaneous reaction.
At 500K, the reaction rate will increase as temperature rises, following the Arrhenius equation. This increase in temperature will also influence the equilibrium position of the reaction if it is a reversible reaction. Higher temperatures can sometimes shift the equilibrium towards the products or reactants, depending on the enthalpy change.
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.
For some non-spontaneous reactions, you can change the temperature. For other non-spontaneous reactions, there is nothing you can do to make it spontaneous. Nature favors reactions that increase a system's entropy (disorder) and nature favors reactions that are exothermic (they release enthalpy). Any reaction that does both of these things is spontaneous at all temperatures. Any reaction that does neither of these things is never spontaneous. As far as this question is concerned, the interesting reactions are endothermic reactions that increase entropy and exothermic reactions that decrease entropy. Whether these reactions are spontaneous depends on the temperature. The first variety (endothermic, increase entropy) will be spontaneous at high temperatures; the second (exothermic, decrease entropy) will be spontaneous at low temperatures. To find the temperature at which a reaction becomes spontaneous, one may apply the Gibbs equation: DG = DH - TDS where capital Ds stand for the Greek capital delta.
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.
It can be + or - depending on the value of the entropy (∆S). Recall, that ∆G = ∆H - T∆S and for a spontaneous reaction, ∆G must be negative, so you can see how this will depend on the values and signs of both enthalpy and entropy.