Why is Combustion exothermic? Don't you usually need to put in energy to start combustion. Eg. Lighting a match to start fire. When you vaporize water to gas, this is endothermic...
Why is combustion an exothermic process?
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Wikipedia the reaction. You put an alkane and o2 to get CO2, H2O and energy as the products.
Also, one way to think about it is that exothermic reactions are ones in which the bonds made by the products are stronger than those of the reactants.
Since you have h-bonding with H2O, those bonds are inevitably gonna be stronger.
Make sense?
Also, one way to think about it is that exothermic reactions are ones in which the bonds made by the products are stronger than those of the reactants.
Since you have h-bonding with H2O, those bonds are inevitably gonna be stronger.
Make sense?
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You need SOME energy input to overcome the activation energy before the combustion can proceed. You need to put in some form of energy to start the exothermic cascade. Hope that clears things up! 🙂
Consider the combustion of glucose:
C6H12O6 + O2 --> 6CO2 + 6H2O + Heat
This reaction is exothermic because energy is a product. The fact a match was lit to start the reaction, or even if the reaction proceeded spontaneously as in spontaneous combustion, is completely irrelevant to the combustion reaction proper, represented by the equation above. The match-lighting reaction is a separate reaction, apart from the glucose reaction.
Undoubtedly the sun is exothermic? But how did it come to be? - unimaginable amounts of energy (much more than a match) must have been invested to start the sun, nonetheless, according to our definition of an exothermic reaction, the sun is indeed exothermic because it produces energy at the present moment, regardless of what the sun was or will be.
When we are talking about combustion, we are thinking of it in its immediate tense, that is, already proceeding and producing energy. How combustion started is a different matter.
C6H12O6 + O2 --> 6CO2 + 6H2O + Heat
This reaction is exothermic because energy is a product. The fact a match was lit to start the reaction, or even if the reaction proceeded spontaneously as in spontaneous combustion, is completely irrelevant to the combustion reaction proper, represented by the equation above. The match-lighting reaction is a separate reaction, apart from the glucose reaction.
Undoubtedly the sun is exothermic? But how did it come to be? - unimaginable amounts of energy (much more than a match) must have been invested to start the sun, nonetheless, according to our definition of an exothermic reaction, the sun is indeed exothermic because it produces energy at the present moment, regardless of what the sun was or will be.
When we are talking about combustion, we are thinking of it in its immediate tense, that is, already proceeding and producing energy. How combustion started is a different matter.
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the products of a combustion reaction have a higher bond energy (collectively) than the reactants so it makes the reaction highly exothermic. think of a combustion engine..the reactions cause an increase temperature (due to heat that is released, making it exothermic) and pressure, and as a result this generates a force to move the engine pistons--->movement of an object
Because the amount of energy that goes into breaking the bond is little compared to the energy given off when the new bonds formed. If you do the bond energy calculations, you will see what I am talking about. Also it's common knowledge when something goes boom, a lot of heat will be given off. Just think of all the stuff you light up like fireworks.
