Explaining why some reactions are spontaneous at certain temperatures

AI Thread Summary
The discussion centers on understanding spontaneity in chemical reactions, specifically through the Gibbs free energy equation ΔG = ΔH - TΔS. A key point is that a spontaneous reaction requires a negative ΔG, which depends on the signs of ΔH and ΔS and the temperature (T). Participants suggest plotting ΔH, -TΔS, and their sum to visualize how these components interact to determine spontaneity. Additionally, plotting temperature against the sum of these values is proposed as a way to understand the relationship better. The conversation highlights the importance of memorizing example reactions to illustrate different types of spontaneity.
ampakine
Messages
60
Reaction score
0
On an exam I got this question:
[PLAIN]http://img849.imageshack.us/img849/5732/spontaneity.png
but at the time I had no idea how to answer it. I still don't really know if I can answer it. I can explain it mathematically with the equation: ΔG = ΔH - TΔS seeing as a spontaneous reaction requires a negative change in G and therefore if the sign of ΔH and ΔS are different then temperature will be a determining factor as to whether or not ΔG will be negative. I have no idea what I would need to plot on a graph though. As for examples of reactions of each type I suppose I needed to have a few example reactions memorised.
 
Last edited by a moderator:
Chemistry news on Phys.org
ampakine said:
I have no idea what I would need to plot on a graph though.

How about plotting ΔH, -TΔS, and their sum?
 
Oh yeah didn't think of that. I could also plot T vs. their sum.
 

Thread 'Solubility of MgSO47H2O in water'

It seems like a simple enough question: what is the solubility of epsom salt in water at 20°C? A graph or table showing how it varies with temperature would be a bonus. But upon searching the internet I have been unable to determine this with confidence. Wikipedia gives the value of 113g/100ml. But other sources disagree and I can't find a definitive source for the information. I even asked chatgpt but it couldn't be sure either. I thought, naively, that this would be easy to look up without...
View full post »

Thread 'Why does having 8 valence electrons make an element inert?'

I was introduced to the Octet Rule recently and make me wonder, why does 8 valence electrons or a full p orbital always make an element inert? What is so special with a full p orbital? Like take Calcium for an example, its outer orbital is filled but its only the s orbital thats filled so its still reactive not so much as the Alkaline metals but still pretty reactive. Can someone explain it to me? Thanks!!
View full post »

Similar threads

Temperature dependence of ΔS°, ΔG° and ΔH°
Replies
1
Views
2K
Temperature range at which a reaction is spontaneous, Where is the mistake?
Replies
5
Views
29K
Half-Reaction Explanations in a Simple Battery
Replies
15
Views
4K
Does ΔG° for reactions vary by temperature?
Replies
6
Views
4K
Chemistry Will this reaction cause an increase or decrease in temperature?
Replies
8
Views
2K
Is Oxyhydrogen a spontaneous reaction at very high temperatures?
Replies
4
Views
3K
Gibbs free energy and entropy inconsistency
Replies
5
Views
2K
A Cause of spontaneous emission?
Replies
15
Views
4K
What is the ΔG for the dilution of aqueous HCl from 0.89 M to 0.253 M at 25°C?
Replies
5
Views
15K
Can Non-Spontaneous Reactions Occur When Coupled with Exergonic Reactions?
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top