Enthalpy and graphs

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Valeria Viera 1B
Posts: 60
Joined: Fri Apr 06, 2018 11:05 am

Enthalpy and graphs

Postby Valeria Viera 1B » Sun Feb 17, 2019 5:42 pm

What is the relationship between enthpy and exothermic/endothermic reactions?
Can any explain the two graphs we saw in class ? (One has a flat line and the other had a curved line)

LorenzoDuvergne3I
Posts: 60
Joined: Fri Sep 28, 2018 12:25 am

Re: Enthalpy and graphs

Postby LorenzoDuvergne3I » Sun Feb 17, 2019 5:53 pm

Endothermic reactions cannot have a positive enthalpy because they need energy to occur, which bars them from being spontaneous.

With regards to the graphs I don't have any answers about that :(

305113590
Posts: 66
Joined: Fri Sep 28, 2018 12:28 am

Re: Enthalpy and graphs

Postby 305113590 » Sun Feb 17, 2019 6:30 pm

If I am referring to the right graph, the flat line is under irreversible, isobaric(constant pressure) conditions where it is defined by w=-P∆V. Lavelle always refers to their being a pin in a piston and once he releases that piston, there is a rapid work of expansion being performed. This is what makes the pressure constant and volume change because the work was irreversible and quick. Conversely, the curved one is a reversible, isothermal process and tends to be slower. Because it is under constant temperature and can be reversible, this is why there is a curve and has more work being done. The area under the curve is a lot more than the flat line.


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