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# Solving for Delta G

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Can you explain what we are doing mathematically, canceling, multiplying etc.? Thank-you.

I am trying to understand how to balance this equation.
We were given the following data to solve for delta G (standard).

S(s) + 3/2 O2(g)--------->SO3(g) delta G standard = -371kJ
2SO2(g)+ O2(g)--------->2SO3(g) delta G standard = -142kJ

Now calculate delta G standard for the reaction.

delta G standard = delta H standard - T delta S standard

Please explain in detail how to balance these two equations together and add. I do not understand where they are getting the 1/2 142 kJ0, and why on the second number we have no coefficient on -371 kJ then we end up with 71kJ - 371 kJ = -300? Could you please explain? Thank-you very much.
Can you explain what they are doing with the 1/2 mathematically? I see now that we are getting rid of the SO3, however how are we doing it? Are we canceling it out?

https://brainmass.com/chemistry/oxidation-reduction-and-electrochemistry/solving-for-delta-g-39287

#### Solution Preview

S(s) + 3/2 O2(g)--------->SO3(g) -371kJ
2SO2(g)+ O2(g)--------->2SO3(g) -142kJ

We need to switch around the second equation so that the SO3 cancels. When we do, we must reverse the sign of the deltaG.

Therefore, we write the following:

S(s) + 3/2 O2(g) --------->SO3(g) ...

#### Solution Summary

The solution provided goes through the steps and explains what each does and why.

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