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Whether or not a reaction occurs is governed by its Gibbs free energy, or spontaneity. We will refer to this as ∆G. When ∆G is less than 0, the reaction is spontaneous and hence it will occur. On the other hand, when ∆G is more than 0, the reaction is not spontaneous and will not take place.
∆G is governed by several factors:
1) ∆H - the enthalpy of the reaction. This is what you mean by reactions that release energy. These energy-releasing reactions are termed as "exothermic reactions".
2) ∆S - the entropy of the reaction.
3) T - the temperature.
They are inter-related with the formula: ∆G = ∆H - T*∆S
Therefore, the enthalpy of a reaction cannot determine its spontaneity as there are other factors (∆S and T) to consider as well. You also have to take note of activation energy barriers that have to be overcome before a reaction can take place!
I hope this was helpful! :)
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∙ 11y ago
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When chemical reactions occur energy is always absorbed?
No, chemical reactions can be endothermic or exothermic.
Chemical reactions that release energy do if occur or don't?
These are called exothermic reactions.
Are exothermic reactions chemical?
Most chemical reactions are exothermic, that is, they release a certain amount of heat as a by-product of the reaction. Endothermic reactions, those which absorb heat, also do occur, but they are more rare. Endothermic reactions are driven by entropy only, whereas exothermic reactions are driven by the energy that is released. The more energy is released, the more easily the reaction will occur.
What is the relationship between the temperature and the rate of chemical?
Heat energy is necessary for some chemical reactions to occur. Some chemical reactions are endothermic meaning they require or absorb energy for a chemical reaction to occur. Other chemical reaction are exothermic meaning they release energy when the chemical reaction takes place..
What two kinds of energy changes can take place during a chemical reaction?
Two types of energy changes that can occur in a chemical reaction are (1) endothermic and (2) exothermic. Endothermic is where energy is added to the system and exothermic is where energy is given off by the system.
What are endothermic exothermic reactions?
Endothermic reactions are reactions that occur when heat is increased or decreased inside a subject. Exothermic is when heat is increased or decreased outside a subject.
What is an another name for exothermic and for endothermic reactions?
it is a Many chemical reactions release energy in the form of heat, light, or sound. These are exothermic reactions. Exothermic reactions may occur spontaneously and result in higher randomness or entropy (ΔS > 0) of the system. They are denoted by a negative heat flow (heat is lost to the surroundings) and decrease in enthalpy (ΔH < 0). In the lab, exothermic reactions produce heat or may even be explosive. There are other chemical reactions that must absorb energy in order to proceed. These are endothermic reactions. Endothermic reactions cannot occur spontaneously. Work must be done in order to get these reactions to occur. When endothermic reactions absorb energy, a temperature drop is measured during the reaction. Endothermic reactions are characterized by positive heat flow (into the reaction) and an increase in enthalpy (+ΔH).
Contrast endothermic and exothermic reactions?
Endothermic reactions are chemical reactions that use heat as part of the reactant. Heat is absorbed into the reaction in order for it to continue. Exothermic reactions are chemical reactions that release heat as a product of the reaction.
What helps chemical reactions occur?
A catalyst helps chemical reactions occur.
What is the resut of a chemical reaction?
Some chemical reactions produce heat, these are called exothermic
How is heat from the sun an exothermic reaction?
Exos= outside , thermos=temperature or heat So within the definition itself it can be known that in exothermic reactions heat is released. In chemical reactions the energy supplied is use in breaking of bonds, but energy is release by making bonds. In exothermic reactions, the energy supplied is sufficient for chemical reaction to occur (to break existing bonds) and the excess energy is given in the form of heat (from making new bonds).If the reaction is exothermic, it means that the total energy it took to break the bonds is less than the total energy released when forming new bonds -- so net energy is released in the form of heat. for example 2H2 +O2 ----> 2H20 which is exothermic reaction. Combustion reactions in general are exothermic reactions.
What else could exothermic and endothermic reactions be used?
They could be used for making science test or other things, per example: Many chemical reactions release energy in the form of heat, light, or sound. These are exothermic reactions. Exothermic reactions may occur spontaneously and result in higher randomness or entropy (ΔS > 0) of the system. They are denoted by a negative heat flow (heat is lost to the surroundings) and decrease in enthalpy (ΔH < 0). In the lab, exothermic reactions produce heat or may even be explosive.
