Enthalpy

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Carla Cruz Medina 1L
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Joined: Fri Sep 25, 2015 3:00 am

Enthalpy

Postby Carla Cruz Medina 1L » Mon Jan 16, 2017 12:07 am

Oxygen difluoride is a colorless, very poisonous gas that reacts rapidly with water vapor to produce O2 and HF and heat:
OF2+H2O->O2+HF2 (DELTA)H=-318kJ

What is the change in internal energy for the reaction of 1 mol OF2?

I know I need to use P(DELTA)V=(DELTA)nRT but the temperature is not given. What do I do?

Hannah_Chao_1D
Posts: 25
Joined: Wed Sep 21, 2016 3:00 pm

Re: Enthalpy

Postby Hannah_Chao_1D » Tue Jan 17, 2017 10:41 am

Since no temperature is given, assume standard conditions. The standard condition for temperature is 298K or 25ºC.

Jennifer_Lam_1A
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Joined: Wed Sep 21, 2016 2:56 pm

Re: Enthalpy

Postby Jennifer_Lam_1A » Wed Jan 18, 2017 5:08 pm

For temperature, should it be in Celsius or Kelvin?

Angela To 2B
Posts: 20
Joined: Wed Sep 21, 2016 2:55 pm

Re: Enthalpy

Postby Angela To 2B » Wed Jan 18, 2017 6:01 pm

The temperature should be in Kelvin because for the P(DELTA)V=(DELTA)nRT equation, the units of R is in J/mol*K !

EmilyLeibovitch2E
Posts: 29
Joined: Wed Nov 18, 2015 3:00 am

Re: Enthalpy

Postby EmilyLeibovitch2E » Sun Feb 05, 2017 5:55 pm

How do you know when to use Kelvin or Celsius in a problem? Can you just always use and convert a question to Kelvin?

Chin_Alyssa_3I
Posts: 34
Joined: Fri Jul 22, 2016 3:00 am

Re: Enthalpy

Postby Chin_Alyssa_3I » Sun Feb 05, 2017 6:58 pm

EmilyLeibovitch2E wrote:How do you know when to use Kelvin or Celsius in a problem? Can you just always use and convert a question to Kelvin?


How you know which unit to use is really dependent on the rest of the values in your problem and their units. Use the other values and units as a guide to help you determine whether to use K or C based on the formulas and given constants

Cris-1C
Posts: 7
Joined: Mon Jan 26, 2015 2:17 pm

Re: Enthalpy

Postby Cris-1C » Sun Feb 12, 2017 11:52 pm

I believe Kelvin is the ideal temperature to be used throughout this problem, although if information and a formula is specified in Celsius, then you most certainly can maintain the units in Celsius. Whichever you use, I believe I've heard my TA say that the key thing is to be consistent throughout a problem.

Gigi Ye 2K
Posts: 9
Joined: Wed Sep 21, 2016 2:55 pm

Re: Enthalpy

Postby Gigi Ye 2K » Thu Feb 16, 2017 9:08 pm

Depending on the problem, it would most likely be in Kelvin. However, you should list out all the units of each value and then eliminate the overlapping units. For example, because the heat capacities have something to do with Celsius then in this case, you should use Celsius.

Michelle Kam 1F
Posts: 10
Joined: Wed Sep 21, 2016 2:58 pm

Re: Enthalpy

Postby Michelle Kam 1F » Sun Feb 26, 2017 5:51 pm

For temperature, it will most likely be K.
However, either is fine if unit is specified in the answer.


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