# I have a couple questions:

1. When analyzing which has greater entropy, do you look at the larger number or the smaller number?

2. What two things must be met for a reaction to be spontaneous under ALL temperature conditions?

3. If heat is in the products, the equation is exothermic right? If heat is in the reactants, the equation is endothermic?

I don't understand question #1.

#2. delta G = delta H - T*delta S

so if delta H is negative and delta S is positive, delta G MUST be negative and the reaction will be spontaneous at all temperatures.

#3. right.

Thanks!

For number 1, for example, if Br2 (l) has a delta S of 152.5 and Br2 (g) has a delta S of 245.4, which one has the greater entropy? Br2 (g) because the number is larger?

Is the delta S of NaCl (aq) included in your table? I was looking for it and I couldn't find it anywhere!

S^{o} at 298.15 (solid) NaCl is 72.38 J/mol*K. Note S is in J while delta G and delta H are in kJ/mol.

I am so sorry, and maybe it is because it is so late, but I'm not understanding anything you previously said. First of all, did you answer the question: For number 1, for example, if Br2 (l) has a delta S of 152.5 and Br2 (g) has a delta S of 245.4, which one has the greater entropy? Br2 (g) because the number is larger? Maybe I just need to stop and look at this stuff tomorrow :)

Secondly, is delta S of NaCl (aq) 298.15? What is 72.38 J/mol*K?

Once again, I am really sorry

You posted no questions about Br2 gas or liquid so I haven't answered anything about that. Second, the 298.15 Kelvin is the TEMPERATURE at which I gave you S^{o} of 72.38 J/mol*K for NaCl (solid). Aqueous NaCl is 115.5 J/mol*K at 298.15 Kelvin

## No problem at all! I apologize for not addressing your questions clearly.

For question #1, to determine which substance has a greater entropy, you need to compare the values of delta S. In your example, if Br2 (l) has a delta S of 152.5 J/mol*K and Br2 (g) has a delta S of 245.4 J/mol*K, then indeed Br2 (g) has a greater entropy. So, in this case, you're correct that the larger number indicates greater entropy.

Regarding your second question, to determine if a reaction is spontaneous under all temperature conditions, we consider the equation delta G = delta H - T*delta S. If delta G is negative, the reaction is spontaneous. For the reaction to always be spontaneous, regardless of temperature, delta G must be negative for all values of T (temperature). This means that both delta H (enthalpy change) and delta S (entropy change) must have specific relationships. Specifically, if delta H is negative (exothermic) and delta S is positive, then delta G will be negative (spontaneous) at all temperatures.

As for your third question, yes, you are right. If heat is a product of the reaction, it is exothermic. Conversely, if it is a reactant, it is endothermic.

Regarding NaCl (aq), the delta S value I provided earlier was for NaCl (solid) at 298.15 Kelvin. I apologize for any confusion caused. The delta S value for NaCl (aq) is different and can be found in the relevant tables or resources for accurate information.

Feel free to ask any further questions or if there's anything else I can assist you with!

## 1. When analyzing which has greater entropy, you should look at the larger value. In your example, Br2 (g) has a delta S of 245.4, which is greater than the delta S of Br2 (l) at 152.5. Therefore, Br2 (g) has a greater entropy.

2. To determine if a reaction is spontaneous under all temperature conditions, two criteria must be met:

a. Delta H (change in enthalpy) must be negative, indicating an exothermic reaction.

b. Delta S (change in entropy) must be positive, indicating an increase in disorder.

If both criteria are fulfilled, delta G (change in Gibbs free energy) will be negative, and the reaction will be spontaneous at any temperature.

3. Your understanding is correct. If heat is a product in the reaction, it is considered an exothermic reaction. Conversely, if heat is a reactant in the equation, it is an endothermic reaction.