4D.7

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805312064
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Joined: Thu Jul 11, 2019 12:16 am

4D.7

Postby 805312064 » Sat Feb 08, 2020 11:02 pm

The question reads:
Oxygen difluoride is a colorless, very poisonous gas that reacts rapidly and exothermically with water vapor to produce O2 and HF:
OF2(g) + H2O(g) -> O2(g) + 2 HF(g) deltaH = -318 kJ
What is the change in internal energy for the reaction of 1.00 mol OF2?

I understand that we have to find q, and to use -delta nRT, but how do you know what the temperature is? The answer key uses 298 Kelvin, but where did that come from?

Thank you in advance!

Jacey Yang 1F
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

Re: 4D.7

Postby Jacey Yang 1F » Sat Feb 08, 2020 11:36 pm

298K is the most common temperature used in data for reaction enthalpies, so we just have to assume that when no temperature is stated.

805312064
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Joined: Thu Jul 11, 2019 12:16 am

Re: 4D.7

Postby 805312064 » Sat Feb 08, 2020 11:46 pm

Thank you! Is this always going to be the case if there is no given temperature?

Ruby Richter 2L
Posts: 103
Joined: Thu Jul 25, 2019 12:17 am

Re: 4D.7

Postby Ruby Richter 2L » Sun Feb 09, 2020 11:34 am

When do you need to change the temperature from celsius to kelvin and when is it okay to leave T as celsius in an equation?

805312064
Posts: 50
Joined: Thu Jul 11, 2019 12:16 am

Re: 4D.7

Postby 805312064 » Sun Feb 09, 2020 12:56 pm

I think if it's ever the difference in T (delta T), then there's no need to convert. However, if you're using T to calculate something else, like in the ideal gas equation, then you need to convert to Kelvin!


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