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Postby Niveda_Tennety_1H » Sat Mar 18, 2017 1:30 pm

When do you use PdeltaV=deltanRT?

Josh Ku 3H
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Re: PdeltaV=deltanRT

Postby Josh Ku 3H » Sat Mar 18, 2017 1:43 pm

You would use this as another way to calculate work when the external pressure is constant.

When Pex is constant, w = -P(delta)V. If the change in volume is not given and say they give you a reaction, then you would look to see if there is a change in the number of gas molecules (delta)n. If so, you can calculate work as: - (delta)n * R * T since as you stated, P(delta)V = (delta)n * R * T. However if there is no change in moles, then you can assume there is no change in volume (as long as temperature is constant as well) and thus there is no work done.

Adrian Lim 1G
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Re: PdeltaV=deltanRT

Postby Adrian Lim 1G » Tue Jan 16, 2018 11:17 pm

Like the reply above stated, it's just a different way to calculate work. We can use - delta n R T if we know the net change in moles of the equation in order to find the work.

MSkye Goldwater 2K
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Re: PdeltaV=deltanRT

Postby MSkye Goldwater 2K » Thu Jan 18, 2018 8:27 pm

You can only use this equation when you are dealing with an ideal gas. The deltas imply that a change is occurring. You can use this in these 2 formulas:

delta H = delta U + nR (delta T)
delta H = delta U + (delta n) RT

Amelia Georgius 1K
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Re: PdeltaV=deltanRT

Postby Amelia Georgius 1K » Mon Jan 22, 2018 9:07 pm

Because w=PdeltaV, work could also be found using w=deltanRT when a value in the other equation is not known. This is because of the equation pV=nRT

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