# Which of these is spontaneous?

1. Feb 10, 2005

### parwana

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.

2. Feb 10, 2005

### GCT

Solve for delta G, find the equation in your text.

3. Feb 12, 2005

### mrjeffy321

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 isnt enough to be spontaneous but it is a good sign, but when enthropy is increasing that does. or am I wrong.

4. Feb 13, 2005

### Gokul43201

Staff Emeritus
That's not right jeffy, spontanaeity is determined by the free energy, not the enthalpy.

5. Feb 13, 2005

### Gokul43201

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