Spontaneous Reactions and Enthelpy

In summary, a spontaneous reaction is a chemical or physical change that occurs without any outside intervention and is driven by the energy of the reactants. The spontaneity of a reaction is affected by entropy and enthalpy, with reactions being more likely to occur spontaneously when there is an increase in entropy or a decrease in enthalpy. Enthalpy is a measure of the total energy of a system and is often associated with the heat exchanged in chemical reactions. The connection between enthalpy and spontaneity is described by the Gibbs free energy equation, which shows that a reaction will be spontaneous if there is a decrease in enthalpy and/or an increase in entropy. Non-spontaneous reactions can become spontaneous under certain conditions, such
  • #1
LordWillO
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Today in AP Chemistry we started learning about entropy and spontaneous reactions. Could someone explain on an undergraduate level (preferably not using calculus) how, if the universe has a fixed amount of mass and energy, that reactions can be spontaneous and create their own energy? Thanks!
 
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  • #2
Reactions don't create energy. There is the first law of thermodynamics which says that energy is conserved. If a reaction is exothermic, heat is given off in the course of the reaction. However this type of energy was stored in the reactands. The products of the reaction have less energy.
 

What is a spontaneous reaction?

A spontaneous reaction is a chemical or physical change that occurs without any outside intervention. It happens on its own, without the need for any additional energy input. In other words, the reactants have enough energy to transform into products without any assistance.

What factors affect the spontaneity of a reaction?

The spontaneity of a reaction is affected by two main factors: entropy and enthalpy. Entropy is a measure of the disorder or randomness in a system, and reactions tend to be more spontaneous when there is an increase in entropy. Enthalpy is the measure of the total energy of a system, and reactions are more likely to be spontaneous when there is a decrease in enthalpy.

What is enthalpy?

Enthalpy is a thermodynamic property that describes the total energy of a system. It includes the internal energy of the system, as well as the energy required to overcome any intermolecular forces. In chemical reactions, enthalpy is often associated with the heat exchanged between the reactants and products.

What is the connection between enthalpy and spontaneity?

The connection between enthalpy and spontaneity is described by the Gibbs free energy equation: ΔG = ΔH - TΔS. This equation shows that the change in free energy (ΔG) is dependent on the change in enthalpy (ΔH) and the change in entropy (ΔS). A reaction will be spontaneous if ΔG is negative, which can happen if there is a decrease in enthalpy (exothermic reaction) and/or an increase in entropy.

Can a non-spontaneous reaction become spontaneous?

Yes, a non-spontaneous reaction can become spontaneous under certain conditions. This can happen if the temperature and/or pressure of the system are changed, or if a catalyst is added. A catalyst can lower the activation energy required for a reaction to occur, making it more likely to happen spontaneously.

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