calculating standard gibbs free energy of reation






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Rachael_1H
Posts: 31
Joined: Fri Sep 25, 2015 3:00 am

calculating standard gibbs free energy of reation

Postby Rachael_1H » Mon Jan 25, 2016 12:08 pm

Calculate standard gibbs free energy of a reaction for the reaction showing the decomposition of mercury (II) oxide at 298 K.

2HgO(s)---> 2Hg(l) + O2(g)

Standard reaction enthalpy of formation for HgO = -90.83
standard molar entropy HgO=70.29, Hg=76.02, and O2=205.14

When finding the standard gibbs free energy of this rxn, I believe that the answer key in our practice quiz booklet changes the Standard RXN Enthalpy of formation of HgO= +90.83

Why is the Standard RXN Enthalpy of formation of HgO made positive?

Fariha Hameed 1D
Posts: 22
Joined: Fri Sep 25, 2015 3:00 am

Re: calculating standard gibbs free energy of reation

Postby Fariha Hameed 1D » Mon Jan 25, 2016 12:25 pm

You make the value positive because you are not forming HgO but rather doing the reverse, which is decomposing 2HgO to make 2Hg and O2. Hope this helps!


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