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### Finding change in internal energy using PV=nRT equation

Posted: Sun Jan 17, 2016 5:54 pm
Hi, I'm looking for help with homework question 8.49, which states,

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

It gives the formula

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?"

I understand that we use the equation PV=nRT to find PV and then find change in internal energy for the rxn by using the equation:
(delta U)=(delta H)-(PV)

I am just confused about what value we use for T when solving for PV using the equation PV=nRT? The answer key has the equation as PV=(1 mole)(gas constant)(298 K)=2.48 kJ. Where did the answer key derive the value T=(298 K) from?

Thanks!

### Re: Finding change in internal energy using PV=nRT equation

Posted: Sun Jan 17, 2016 5:58 pm
298 Kelvin is the same as 25 Celsius, the standard temperature that is typically used in various equations and formulas. Hope this helped.

### Re: Finding change in internal energy using PV=nRT equation

Posted: Sun Jan 17, 2016 6:13 pm
I'm guessing that they may have left out the information for the temperature at which the reaction took place in the textbook. Usually, the temperature would be given in the problem.

### Re: Finding change in internal energy using PV=nRT equation

Posted: Wed Feb 12, 2020 10:58 am
Since the reaction doesn't specify, we can assume T=298K (room temperature). However, this is a typo on the textbook's part; they should have specified T.