Calculating Enthalpy
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Calculating Enthalpy
In addition to Hess's Law, what are the other 2 methods to calculate the enthalpy of a reaction? Also, would we only use the other methods if we are not given the enthalpy change at each step of a reaction?
Re: Calculating Enthalpy
Hi,
The other two methods include using bond enthalpies (the energy required to break the bonds + the energy released from product formation) and subtracting the standard enthalpy of reactants from products. I think you normally use the bond enthalpies methods when you don't know the values for the other two methods because it is the least accurate.
The other two methods include using bond enthalpies (the energy required to break the bonds + the energy released from product formation) and subtracting the standard enthalpy of reactants from products. I think you normally use the bond enthalpies methods when you don't know the values for the other two methods because it is the least accurate.
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Re: Calculating Enthalpy
I agree with the previous answer, another possible method 4 is figuring it out through experimentation.
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Re: Calculating Enthalpy
The other methods include subtracting the standard enthalpy of reactants from products, or using bond enthalpies to see the energy difference.
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Re: Calculating Enthalpy
Hi!
There is also the method of bond enthalpies, which may be used when you know the enthalpies of the individual bonds that make up the reactants and products. We did one example in class (1/27 lecture) like this where we drew out the lewis structure of the reactants and products to reveal the bonds, and were given the bond enthalpies. Then we subtracted the reactant enthalpies from the products. The other method is using standard states to use the standard enthalpy of formation of all products and subtracting the standard enthalpy of formation of the reactants to get the net enthalpy of the reaction. Hope this helps!
There is also the method of bond enthalpies, which may be used when you know the enthalpies of the individual bonds that make up the reactants and products. We did one example in class (1/27 lecture) like this where we drew out the lewis structure of the reactants and products to reveal the bonds, and were given the bond enthalpies. Then we subtracted the reactant enthalpies from the products. The other method is using standard states to use the standard enthalpy of formation of all products and subtracting the standard enthalpy of formation of the reactants to get the net enthalpy of the reaction. Hope this helps!
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