## Enthalpy

Carla Cruz Medina 1L
Posts: 12
Joined: Fri Sep 25, 2015 3:00 am

### Enthalpy

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

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

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

### Re: Enthalpy

For temperature, should it be in Celsius or Kelvin?

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

### Re: Enthalpy

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

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

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

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

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

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