## 4D.7

Dina 2k
Posts: 57
Joined: Wed Sep 18, 2019 12:17 am

### 4D.7

Not sure if this question has been asked, but the problem states: "Oxygen difluoride is a colorless, very poisonous gas that reacts rapidly and exothermically with water vapor to produce 02 and HF. Delta H= -1368 kJ. What is the change in internal energy for the reaction of 1 mol of OF2?" I understand that delta U= Delta H-PDeltaV, but to find P delta V, you need to find temperature? how did they get 298K as the temp? is it because the standard entropy of a substance is the entropy of 1 mol at 298K?

KBELTRAMI_1E
Posts: 108
Joined: Sat Jul 20, 2019 12:17 am

### Re: 4D.7

I believe that Lavelle mentioned that when it doesn't specifically state a temp, we typically assume its 25 degrees C which is 298K. However, I'm not sure if you need to know the temp for this problem.

Baoying Li 1B
Posts: 113
Joined: Sat Aug 17, 2019 12:18 am

### Re: 4D.7

For this question, delta U = q + w since it does not specifically indicate the specific process. When you calculate w=-delta n RT, you would need the temperature, which is 298 K (we usually assume that the reaction is in standard temperature if it does not indicate).