Which of These Reactions Are Spontaneous?

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Discussion Overview

The discussion revolves around identifying which of several chemical reactions are spontaneous under constant temperature and pressure conditions. Participants analyze the relationships between enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) to determine spontaneity, with a focus on the implications of these thermodynamic properties.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that choice (a) is spontaneous because it is exothermic and has an increase in entropy, questioning if this reasoning is correct.
  • Another participant counters that spontaneity is determined by Gibbs free energy rather than just enthalpy or entropy alone.
  • Several participants express uncertainty about the criteria for spontaneity, particularly regarding the roles of enthalpy and entropy in the context of Gibbs free energy.
  • One participant reiterates the need to calculate ΔG using the appropriate equation, indicating a reliance on textbook knowledge.

Areas of Agreement / Disagreement

Participants do not reach a consensus on which reactions are spontaneous, with multiple competing views on the factors influencing spontaneity. The discussion remains unresolved regarding the correct application of thermodynamic principles.

Contextual Notes

Participants reference the need for specific calculations involving Gibbs free energy but do not provide the necessary equations or steps, leaving some assumptions and mathematical processes unaddressed.

parwana
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Which of these is spontaneous??

Which of the following are spontaneous at constant T and P ?


(a) DH = -10 KJ DS = +5 J/K T = 298K

(b) DH = +5 KJ DS = -5 J/K T = 10K

(c) DH = -10 KJ DS = -40 J/K T = 300K

(d) DH = -10 KJ DS = -40 J/K T = 200K

(e) DH = -10 KJ DS = -40 J/K T = 500K


DH= enthalpy

DS= entropy

all i know about spontaneous reactions is that entropy is greater than zero, and gibbs free energy is negative. Help with this one.
 
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Solve for delta G, find the equation in your text.
 
isnt it choice "A", since that one is giving off energy (exothermic) and it is becomming more dissordered (enthropy is increasing). All the rest are either taking in energy (endothermic) and/or enthropy is decreasing.
just being exothermic itself isn't enough to be spontaneous but it is a good sign, but when enthropy is increasing that does. or am I wrong.
 
That's not right jeffy, spontanaeity is determined by the free energy, not the enthalpy.
 
parwana said:
Which of the following are spontaneous at constant T and P ?


(a) DH = -10 KJ DS = +5 J/K T = 298K

(b) DH = +5 KJ DS = -5 J/K T = 10K

(c) DH = -10 KJ DS = -40 J/K T = 300K

(d) DH = -10 KJ DS = -40 J/K T = 200K

(e) DH = -10 KJ DS = -40 J/K T = 500K


DH= enthalpy

DS= entropy

all i know about spontaneous reactions is that entropy is greater than zero, and gibbs free energy is negative. Help with this one.

You've virtually been told everything you need to do. I can't imagine where your difficulty lies.
 

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