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Finding change in internal energy using PV=nRT equation

Posted: Sun Jan 17, 2016 5:54 pm
by Rachael_1H
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
by 204643643
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
by Austin Vo 1K
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
by Leonardo Le Merle 1D
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.