### 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!

"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!