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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: hya_been on December 28, 2005, 03:32:23 PM

Title: Hess' Law
Post by: hya_been on December 28, 2005, 03:32:23 PM

Hello I'm trying to find the molar enthalpy change of the following reaction (where A,B,C,D,E,F,G are all compounds)

target reaction: 3A(aq) + B(aq) --> 2D(g)

Given: A(aq) + G (aq) --> F(aq) ?H = -375 kJ/moL
          B(aq) + 2F(aq) --> C(aq) ?H = -122kJ/moL
?Hf B(aq) =  -47 kJ/mol
?Hf C(aq) = -125 kJ/mol
?Hf D(g) = -290 kJ/mol
?Hf G(aq) =  +25 kJ/ml

I cannot for the life of me figure out how I can cancel these equations out (using Hess's law) to get the target reaction how do I add 'D' in using the enthalpy of formation values.

Title: Re:Hess' Law
Post by: Donaldson Tan on December 29, 2005, 12:14:32 AM

heat of reaction = sum of enthalpy of formation for products - sum of enthalpy of formation for reactants.