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Bond enthalpy not given

Posted: Wed Jan 30, 2019 10:24 am
by 505095793
If the bond enthalpy is not given how would we calculate the reaction enthalpy?

Re: Bond enthalpy not given

Posted: Wed Jan 30, 2019 10:45 am
by Manya Bali 4E
There are two other ways. One is that the enthalpy of the reaction equals the sum of the enthalpies of formations of the products minus the sum of the enthalpies of formation for the products. The other way is to use Hess's method and add together the enthalpies of different reactions if, together, the reactions form the reactants/products you want.

Re: Bond enthalpy not given

Posted: Wed Jan 30, 2019 11:18 am
by LorenzoDuvergne3I
It should be noted that the other two methods also require some sort of given information, either the enthalpies of formation or the enthalpies of each reaction, so which method you use depends on what information the problem gives you.

Re: Bond enthalpy not given

Posted: Wed Jan 30, 2019 12:15 pm
by Clarissa Cabil 1I
If a certain bond enthalpy is not given, also note if the bond is between elemental molecules at their most natural state at standard conditions (E.g. O2 (g), F2 (g)) in which the bond enthalpy is assumed to be equal to 0.

Hope this helps!