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

© BrainMass Inc. brainmass.com July 22, 2018, 2:36 pm ad1c9bdddf

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 ...