Explore BrainMass

Free energy equation - The relationship between dG=dH-TdS (d stands for delta)

I'm having trouble understanding the 2nd law of thermodynamics in it's relationship to entropy. This is probably the reason why i can't seem to grasp the components of the free energy equation dG=dH-TdS

What i do know is this, that if dG<0 the reaction is spontaneous (exergonic)
and if dG>0 the reactions is nonspontaneous (endergonic)
how the other components fit into the picture is where i am confused.

i would like to be in a position to know if one variable increase or decreases how dose it effect dG.

I'm going to show you a couple of questions below that i got wrong on an exam to show you where i stand on this subject.
Also i would greatly appreciate it if you can avoid being technical in your response because i tried reading my textbook 100 time to understand this topic and it's not working, so another approach my help for me.
Thank you for your time

Here are the questions i got wrong. (this is just to give you a guideline on where i stand on this subject)

1.According to the second law of thermodynamics, which of the following is true?
MY answer: All reactions produce some heat.
The correct answer: The ordering of one system depends on the disordering of another.

7. If the entropy of a system is increasing, this means that ____________.
MY answer: the amount of usable energy in the system is increasing
The correct answer: energy input will be needed to maintain organization

15. If, during a process, the system becomes more ordered, then ____________.
My answer: dG is positive
The correct answer: TdS is negative

17. When one molecule is broken down into six component molecules, which one of the following is definitely true?
MY answer: dH is negative.
The correct answer: dS is positive.

Once again thank you for your help

Solution Preview

Hello and thank you for posting your question to Brainmass!

My explanation is attached below (next to the paperclip icon) in two formats. one is ...