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Q: Why endothermic reactions cannot be spontaneous reactions?
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How can an endothermic reaction be spontaneous at room temperature?

Exothermic, as endothermic reactions require activation energy.


On what conditions does a spontaneous reaction become spontaneous?

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.


Is spontaneous reaction exo or endo?

Reactions are described by this equation: GD = HD - TDS where D = delta for change in values. GD < 0 spontaneous HD < 0 exothermic ; HD > 0 endothermic The first equation is Gibbs free energy. When G is negative, the reaction is spontaneous. In contrast, a positive number G is non spontaneous. The interesting thing is that spontaneous reactions can be EITHER exothermic and endothermic. Lets look at this: lets assume HD has a value of 100. This means TDS would have to be bigger than 100 in order to make GD a negative number. An endothermic reaction which has a positive H can still be exothermic. Here's another way to pose your question: Is an exothermic reaction spontaneous? Always. Is an endothermic reaction spontaneous? This can be either.


What are some examples of endothermic reactions that are endothermic as well?

All ENDOthermic reactions are of course ENDOthermic by themselves, aren't they?


A chemical reaction that requires a net input of energy?

"Activation Energy reactions"; Endothermic reactions require energy.


Are endothermic reactions always nonspontaneous?

No, many exothermic reactions need the heat of activation to start the reaction. Paper, for instance, does not spontaneously burst into flame... you need to raise its temperature to the kindling point for it to burn.


How do chemical reactions that absorbs energy are called?

Endothermic reaction = absorbs energyExothermic reaction = releases energy


Which reactions requires or stores energy?

Endothermic reactions require energy while exothermic reactions release energy.


Reactions that release heat as bonds are broken are called .?

exothermic


How do you use the word endothermic in a sentence?

Most endothermic reactions will stop once the temperature becomes too low. Stars cannot make energy from fusing iron into nickel since it is an endothermic process.


Differentiate exothermic from endothermic reactions?

Exothermic reactions give out heat; Endothermic ones absorb heat.


Is combustion exothermic or endothermic?

exothermic reactions are the reactions which give out heat and endothermic reactions are the reaction which absorb heat.so combustion is an exothermic reaction.