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AS Chemistry endo and exo help

Hi there,

I'm just getting a bit confused.

If bond breaking is endothermic, and bond making is exothermic.

Why is the definition of an endothermic reaction in my textbook:

" A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants."

Thanks for any help.
Reply 1
Avatar for clownfish
clownfish
10
Original post by IndyJK9
Hi there,

I'm just getting a bit confused.

If bond breaking is endothermic, and bond making is exothermic.

Why is the definition of an endothermic reaction in my textbook:

" A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants."

Thanks for any help.


As more energy was taken in to break the bonds in the reactants than was given out in making the bonds in the products. So the reactants are at a lower energy than the products.
Reply 2
Avatar for IndyJK9
IndyJK9
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Original post by clownfish
As more energy was taken in to break the bonds in the reactants than was given out in making the bonds in the products. So the reactants are at a lower energy than the products.


Thank you. I think I get it now. So it's about the level they're at rather than the enthalpy change?
Reply 3
Avatar for clownfish
clownfish
10
Original post by IndyJK9
Thank you. I think I get it now. So it's about the level they're at rather than the enthalpy change?


Well both. If the reactants are at a lower energy level than the products, then the energy change (or enthalpy change) will be positive for the reaction, so therefore endothermic.

Enthalpy change = energy of products-energy of reactants.

Perhaps take a look at here, it might make it clearer :smile: http://www.knockhardy.org.uk/sci_htm_files/08enth.pdf
Reply 4
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illusionz
20
And I came here all excited about someone potentially asking about the diels-alder reaction :frown:
Reply 5
Avatar for clownfish
clownfish
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Original post by illusionz
And I came here all excited about someone potentially asking about the diels-alder reaction :frown:


They don't tend to cover it in AS chemistry :tongue:
Reply 6
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illusionz
20
Original post by clownfish
They don't tend to cover it in AS chemistry :tongue:


mmmm I realised :tongue:
Reply 7
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IndyJK9
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2
Original post by illusionz
And I came here all excited about someone potentially asking about the diels-alder reaction :frown:


Sorry to disappoint.

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