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Lewis structures

Posted: Sun Mar 15, 2020 11:19 pm
by Abigail Menchaca_1H
How can you tell if a reaction is endothermic or exothermic with just the lewis structures of the species?

Re: Lewis structures

Posted: Sun Mar 15, 2020 11:23 pm
by PranaviKolla2B
It is based on the bonds formed and the bonds that are broken. I believe it is (but can someone confirm): the more bonds that are formed - the more exothermic; the more bonds broken - the more endothermic (generally, not always).

Re: Lewis structures

Posted: Mon Mar 16, 2020 12:20 am
by Adam Kramer 1A
Based on Lewis structures, we know that it takes energy to break a bond, and energy is released to form bonds, so if bonds are being made then the reaction is endothermic, since it is taking in energy, and it bonds are being broken then it is exothermic, since energy is being released.

Re: Lewis structures

Posted: Mon Mar 16, 2020 8:57 am
by Diana A 2L
You would calculate the enthalpies of formation of the substances, and then subtract the enthalpy of the reactants from the enthalpy of the products to see if you get a positive or negative value. Negative, it'll be exothermic, positive endothermic.

Re: Lewis structures

Posted: Mon Mar 16, 2020 11:55 am
by Charysa Santos 4G
If bonds are being broken, then that is endothermic (requires energy), but if bonds are being made then that is generally exothermic (releases energy).