Spontaneous?


Moderators: Chem_Mod, Chem_Admin

Valeria Viera 1B
Posts: 60
Joined: Fri Apr 06, 2018 11:05 am

Spontaneous?

Postby Valeria Viera 1B » Sun Feb 24, 2019 8:30 pm

How do you know if delta S, H, or G are spontaneous?

Jaqueline Monreal 2L
Posts: 57
Joined: Fri Sep 28, 2018 12:28 am

Re: Spontaneous?

Postby Jaqueline Monreal 2L » Sun Feb 24, 2019 9:05 pm

they are usually spontaneous if they're values are negative, meaning they are releasing energy

Dhwani Krishnan 1G
Posts: 63
Joined: Fri Sep 28, 2018 12:17 am

Re: Spontaneous?

Postby Dhwani Krishnan 1G » Sun Feb 24, 2019 9:07 pm

Enthalpy doesn't really show spontaneity, except that exothermic reactions are generally spontaneous because delta S is usually positive for these reactions.

A positive entropy generally indicates a spontaneous process, but only with a negative delta G can you be sure.

Ariel Cheng 2I
Posts: 67
Joined: Fri Sep 28, 2018 12:29 am

Re: Spontaneous?

Postby Ariel Cheng 2I » Sun Feb 24, 2019 9:18 pm

I think the only way to be sure of spontaneity is when ΔG is negative (when ΔH −TΔS is negative) though I could be wrong.

Sheridan Slaterbeck 1J
Posts: 62
Joined: Fri Sep 28, 2018 12:27 am

Re: Spontaneous?

Postby Sheridan Slaterbeck 1J » Sun Feb 24, 2019 10:12 pm

It is spontaneous if delta G is negative, if (-TdeltaS) is negative, if deltaS is positive, and if delta H is negative
delta G = deltaH -TdeltaS

Sheridan Slaterbeck 1J
Posts: 62
Joined: Fri Sep 28, 2018 12:27 am

Re: Spontaneous?

Postby Sheridan Slaterbeck 1J » Sun Feb 24, 2019 10:13 pm

When delta G is negative it is exergonic and when it is positive it is endergonic
when delta H is negative it is exothermic and when it is positive it is endothermic.

505211599
Posts: 60
Joined: Fri Sep 28, 2018 12:28 am

Re: Spontaneous?

Postby 505211599 » Sun Feb 24, 2019 10:22 pm

You can only know for sure if a process is spontaneous if delta G is negative.

Mariana Fuentes 4l
Posts: 21
Joined: Wed Nov 15, 2017 3:00 am

Re: Spontaneous?

Postby Mariana Fuentes 4l » Sun Feb 24, 2019 10:29 pm

if delta s is positive the process will be spontaneous.
if delta g is negative then it is exergonic meaning that it is spontaneous in the forward direction.
if delta g is greater than 0 it is spontaneous in the reverse direction.
delta h <0 and delta s>0 spontaneous
delta h<0 and delta s spontaneous if temperature is low

Jacob Bershatski 4C
Posts: 30
Joined: Fri Sep 28, 2018 12:21 am

Re: Spontaneous?

Postby Jacob Bershatski 4C » Sun Feb 24, 2019 10:33 pm

Enthalpy cannot be used to determine spontaneity. By definition, a negative deltaG means a reaction is spontaneous. A positive deltaS I assume would also be considered spontaneous in most cases according to the Second Law of Thermodynamics.

Aiden Atoori 1C
Posts: 67
Joined: Fri Sep 28, 2018 12:24 am

Re: Spontaneous?

Postby Aiden Atoori 1C » Sun Feb 24, 2019 10:45 pm

You can determine if it’s spontaneous depending on whether delta G is negativeness or not.

isarose0
Posts: 62
Joined: Fri Sep 28, 2018 12:15 am

Re: Spontaneous?

Postby isarose0 » Sun Feb 24, 2019 11:57 pm

if delta G is negative, the reaction is spontaneous, if delta G is positive it is nonspontaneous

AnnaYan_1l
Posts: 96
Joined: Fri Apr 06, 2018 11:05 am
Been upvoted: 1 time

Re: Spontaneous?

Postby AnnaYan_1l » Mon Feb 25, 2019 12:09 am

When delta G is negative, it is spontaneous

Jack DeLeon 1B
Posts: 30
Joined: Fri Sep 28, 2018 12:20 am

Re: Spontaneous?

Postby Jack DeLeon 1B » Mon Feb 25, 2019 12:30 am

with a negative deltaG, it indicates that the second state of the reaction, in other words the products, are favored so therefore the reaction is spontaneous

Rehan Chinoy 1K
Posts: 67
Joined: Fri Sep 28, 2018 12:25 am

Re: Spontaneous?

Postby Rehan Chinoy 1K » Mon Feb 25, 2019 1:05 pm

I think there is some general confusion about what spontaneity is. "Spontaneous" describes a process or reaction, so values of delta H, G, or S themselves cannot be spontaneous, but they can be used to prove spontaneity through the equation Delta G = Delta H - Temp(Delta S). The process is spontaneous when Delta G is negative.


Return to “Work, Gibbs Free Energy, Cell (Redox) Potentials”

Who is online

Users browsing this forum: No registered users and 2 guests