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Reaction Feasibility- Gibbs Equation Question

https://isaacphysics.org/questions/reaction_feasibility?stage=all

I've done part B, but not sure why I'm getting part A wrong. If the change in entropy is x and the change in enthalpy is y, at a temperature T, then G=y-xT. Then for a spontaneous reaction, G<0 so y-xT<0. But Isaac Physics says this is wrong. I don't know where I've went wrong so any help would be appreciated.

Edit: I meant to post this in the chemistry forum instead of the maths one, how do I change this?
(edited 1 year ago)
Original post by Ice.Log
https://isaacphysics.org/questions/reaction_feasibility?stage=all

I've done part B, but not sure why I'm getting part A wrong. If the change in entropy is x and the change in enthalpy is y, at a temperature T, then G=y-xT. Then for a spontaneous reaction, G<0 so y-xT<0. But Isaac Physics says this is wrong. I don't know where I've went wrong so any help would be appreciated.

Edit: I meant to post this in the chemistry forum instead of the maths one, how do I change this?


Report - Posting help - Move thread
Ive reported it for you, but thats for the future.
Reply 2
Thank you for moving the forum
Original post by mqb2766
Report - Posting help - Move thread
Ive reported it for you, but thats for the future.
Reply 3
Anyone?
You are correct that that there should be a y - Tx, as ΔG = ΔH - TΔS (where ΔH is y and ΔS is x) but remember a reaction is feasible if ΔG is less than or equal to 0. So how might you refine your answer in light of this?
(edited 1 year ago)
Reply 5
So y-Tx is less than or equal to zero. I put that on Isaac Physics but it still shows incorrect. Also isn't delta S equal to x, not T?
(edited 1 year ago)
Original post by Ice.Log
So y-Tx is less than or equal to zero. I put that on Isaac Physics but it still shows incorrect. Also isn't delta S equal to x, not T?

Correct, typo on my end (I’ve had 30 mins of sleep lol).

Yeah I’ve tried it a few times and IsaacPhysics doesn’t like it. I’d say move on and just learn the fact that over a range of temperatures where a reaction is feasible, ΔH - TΔS is less than or equal to 0
(edited 1 year ago)
Reply 7
Original post by TypicalNerd
Correct, typo on my end (I’ve had 30 mins of sleep lol).

Yeah I’ve tried it a few times and IsaacPhysics doesn’t like it. I’d say move on and just learn the fact that over a range of temperatures where a reaction is feasible, ΔH - TΔS is less than or equal to 0

Fair enough, I might email Isaac Physics about it and see what's going on. Thanks for the help.
Reply 8
I realised the question wanted me to consider entropy instead of Gibbs free energy. So the total entropy>0 which means entropy of surroundings + entropy of system>0. And entropy of surroundings = -y/T (negative sign due to heat flowing into surroundings) so I got -y/T+x>0. It's the same as the answer I got initially, but for some reason Isaac Physics didn't accept that form.

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