## 4D.7: Finding change in internal energy through ideal gas equation

Hannah Lee 2F
Posts: 117
Joined: Thu Jul 11, 2019 12:15 am

### 4D.7: Finding change in internal energy through ideal gas equation

Oxygen difluoride is a colorless, very poisonous gas that reacts rapidly and exothermically with water vapor to produce O2 and HF:

OF2 (g) +H20 (g) --> O2 (g) + 2HF (g) with delta H being -318 kJ.

What is the change in internal energy for the reaction of 1.00 mol OF2?

Do you assume that external pressure is constant unless it is explicitly stated that it changes? (because otherwise you can't use the ideal gas equation) And how are you supposed to use ideal gas equation to find change in internal energy?

I'm also confused as to why the question didn't mention the temperature of the reaction, since it's needed for the ideal gas equation.

Jordan Young 2J
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### Re: 4D.7: Finding change in internal energy through ideal gas equation

Because the change in thermal energy is equal to q + w and since there isn't any work being done on the system, I believe that the answer is simply delta U = q and q = delta H so the answer is -320 because that is the value of delta H in the reaction for 1 mol of OF2.

BNgo_2L
Posts: 95
Joined: Wed Sep 11, 2019 12:17 am

### Re: 4D.7: Finding change in internal energy through ideal gas equation

Since there is no work being done on the system, delta U = q, and q = deltaH x n, where n = moles. Therefore deltaU = -318 x 1.00 mol OF2.

Amy Xiao 1I
Posts: 101
Joined: Sat Jul 20, 2019 12:15 am

### Re: 4D.7: Finding change in internal energy through ideal gas equation

Jordan Young 2J wrote:Because the change in thermal energy is equal to q + w and since there isn't any work being done on the system, I believe that the answer is simply delta U = q and q = delta H so the answer is -320 because that is the value of delta H in the reaction for 1 mol of OF2.

Where did you get the 320? They only give the 318, so where are the additional 2 kJ from?

Jordan Young 2J
Posts: 102
Joined: Thu Jul 25, 2019 12:17 am
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### Re: 4D.7: Finding change in internal energy through ideal gas equation

I think it might be because of significant figures

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