Enthalpy Units

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bonnie_schmitz_1F
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Enthalpy Units

Postby bonnie_schmitz_1F » Sat Jan 26, 2019 5:13 pm

What are the units for enthalpy? Sometimes its written in kJ but other times its kJ mol-1. Is there a difference?

emily gao 1C
Posts: 61
Joined: Fri Sep 28, 2018 12:29 am

Re: Enthalpy Units

Postby emily gao 1C » Sat Jan 26, 2019 5:53 pm

enthalpy is in some kind of joules (J, kJ, etc). kJ/mol is just per mole what is the enthalpy
aka its not too significant

Helen Zhao 1F
Posts: 31
Joined: Fri Sep 28, 2018 12:20 am

Re: Enthalpy Units

Postby Helen Zhao 1F » Sat Jan 26, 2019 7:13 pm

Enthalpy is the amount of heat released or absorbed at constant pressure. Whether or not it's kJ or kJ * mol^-1, it doesn't really matter. Just remember to use the units that best fits the question asked.

Simmi Diwanji 2B
Posts: 32
Joined: Fri Sep 28, 2018 12:20 am

Re: Enthalpy Units

Postby Simmi Diwanji 2B » Sat Jan 26, 2019 8:50 pm

I think enthalpy could be either kJ or kJ/mol but the standard enthalpy of formation always must be kJ/mol.

maldonadojs
Posts: 57
Joined: Fri Sep 28, 2018 12:27 am

Re: Enthalpy Units

Postby maldonadojs » Sat Jan 26, 2019 8:55 pm

I do not believe that there is a difference, but it follows the information given by the problem.

Anjali_Kumar1F
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Joined: Fri Sep 28, 2018 12:25 am

Re: Enthalpy Units

Postby Anjali_Kumar1F » Sat Jan 26, 2019 10:29 pm

What is the standard enthalpy of formation?

Simran Rai 4E
Posts: 58
Joined: Fri Sep 28, 2018 12:17 am

Re: Enthalpy Units

Postby Simran Rai 4E » Sat Jan 26, 2019 11:54 pm

The standard enthalpy of formation is the enthalpy change when 1 mole of a substance is formed from its element(s). Note that all the substances should be in standard state.

ran2000
Posts: 66
Joined: Fri Sep 28, 2018 12:15 am

Re: Enthalpy Units

Postby ran2000 » Sun Jan 27, 2019 3:22 pm

It depends on the situation. When considering a free reaction, we consider kJ since that is the exact amount of energy being released or absorbed. But, when we consider the situation where in we are considering a standard reaction (ex: Haber's process for 1 mol of ammonia), then we write kJ mol-1 to indicate the energy per unit.


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