+VE and phase change

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Andre Tsivis 1K
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+VE and phase change

Postby Andre Tsivis 1K » Fri Jan 08, 2016 1:51 am

I am a little unsure of what the term "+VE" (Course reader Pg 17) means. Also, if VE+ is the result of endothermic reactions, could the term change to be negative in the case of exothermic state changes (e.g. freezing/condensation/deposition), or does state change only yield a positive VE+ result?

Chem_Mod
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Re: +VE and phase change

Postby Chem_Mod » Fri Jan 08, 2016 2:10 am

+ve and -ve are Prof Lavelle's shorthand for positive and negative. Endothermic is a positive enthalpy value. For the reverse reaction it would be exothermic and negative.

Peter 14B
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Re: +VE and phase change

Postby Peter 14B » Fri Jan 08, 2016 2:12 am

I don't know what VE stands for, but it is true that VE means energy. As can be seen from the first equation, Delta H(vap) does yield positive value since there must be an input of energy(+VE) to the substance. And yes, if the process was backward - vapor to liquid - then it would be exothermic and it would have -(negative) VE value.


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