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Postby annikaying » Sun Feb 09, 2020 8:37 pm

What is the relationship between work and heat when calculating enthalpy? Not just a formula but conceptually what it means.

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Re: enthalpy

Postby PranaviKolla2B » Sun Feb 09, 2020 8:43 pm

Also, what does it mean that enthalpy is always heat but heat is not always enthalpy?

Eesha Chattopadhyay 2K
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Re: enthalpy

Postby Eesha Chattopadhyay 2K » Sun Feb 09, 2020 8:43 pm

The sum of the work done on/by a system and the heat given off/absorbed by a system is equal to the enthalpy of a reaction. This being said, when there is a constant pressure, the delta H value is simply equal to the heat transfer.

Hussain Chharawalla 1G
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Re: enthalpy

Postby Hussain Chharawalla 1G » Sun Feb 09, 2020 8:57 pm

A slight correction to the previous definition. I believe that the sum of work and heat given off in a reaction is equal to change in internal energy (U). Enthalpy is related to heat given off in a reaction during a constant pressure. The heat given off in a reaction is generally denoted by q but in conditions of constant pressure (qp) this is enthalpy. Heat exchanged (q) is an overarching concept and the heat exchanged under a constant pressure condition is enthalpy.

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