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Postby Jaime_Chamberlain_3G » Sun Jan 22, 2017 3:56 pm

How would you go about doing number 49 for the chapter 8 homework? "Oxygen difluoride is a colorless, very poisonous gas that reacts rapidly with water vapor to produce O2, HF, and heat: OF2(g)+H2O(g)--> O2(g)+2HF(g) deltaH=-318J What is the change in internal energy for the reaction of 1.00 mol OF2?"

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Re: 8.49

Postby Lily_Dermendjian_2B » Sun Jan 22, 2017 4:25 pm

You use the equation deltaU=q+w. You can use the given deltaH for q, and use the equation w=-PdeltaV=-deltanRT to find w. This gives you deltaU=q+w=deltaH-PdeltaV=-318kJ-2.48kJ=-320kJ.

Sunny Chera 1N
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Re: 8.49

Postby Sunny Chera 1N » Sun Jan 22, 2017 4:30 pm

For this problem, you must look at the balanced equation and determine the change in moles, delta(n)=nfinal-ninitial. In this case, nfinal would be 3 moles since there are 3 moles on the products side of the equation, and ninitial would be 2 moles, as there are two moles on the reactants side of the equation. Therefore, delta(n)=3-2=+1 mol. Then you use the relationship between delta(H) and delta(U): delta(H)=delta(U)+delta(n)gas*R*T. You know that delta(H)=-318 kJ as listed in the problem for the reaction. Now you isolate that relationship for delta(U) to get -320 kJ as your change in internal energy!

Let me know if you need any further elucidation regarding any aspect of this problem!


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Re: 8.49

Postby ntyshchenko » Sun Jan 22, 2017 9:38 pm

What would you plug in for T in this equation?

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