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And if you work out the energetics as we've gone with thermochemistry, dH you discover there's a huge negative delta H.
如果你计算能量变化,就像在化学热力学中所作的一样，你会发现很大的负的。
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This is just an equality. I have a constant pressure dH process. This term here is equal to zero.
这是一个等式，这是个恒压过程,这项等于零，这意味着。
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So, these two are equal to each other as well which tells me that this derivative, Cp dH/dT constant pressure is Cp.
所以这两者也相等,这告诉我们在恒压下微分，等于。
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If you want to have an infinitestimally small change, you end up writing dh is dq sub p.
这是对于有限的变化而言的,如果是一个无限小的变化。
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So for an ideal gas then, dH/dp under 0 constant temperature, that has to be equal to zero.
所以对于理想气体,偏H偏p在恒温下，等于。
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but right now you're going to have to take it for granted. So, if the Joule-Thomson coefficient is equal to zero, just like we wrote, du = Cv dT du = Cv dT for an ideal gas, we're going to dH = Cp dT have dH = Cp dT for an ideal gas as well.
但是现在请你们应该把它看成理所当然的,所以，如果焦耳-汤姆逊系数等于零,就像我们写的，对于理想气体,我们也可以得到对于理想气体。
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dH STUDENT: dH.
学生：
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p This is going to get us dH/dp constant temperature. What is this experiment?
这帮助我们理解恒温条件下的偏H偏,那么这个实验具体是什么呢？
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Vdp So dH is just du plus p dV plus V dp.
所以dH等于du加上pdV再加上。
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Therefore, from experiments, u is only a function of temperature for an ideal gas, H and therefore from these experiments, 0 we come out with delta H dH/dp is equal to zero.
因此，从实验可以得出,对于理想气体u只是温度的态函数，因此从这些实验中我们得到Δ,偏H偏p等于。
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What is dH/dT as a function, keeping pressure constant, what is dH/dp, keeping temperature constant?
恒定时偏H偏T是什么,温度恒定时的偏H偏p又是什么呢？,好的，让我们解决第一个问题？
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So we already know that. So now we can write CpdT or differential dH as Cp dT plus dH/dp, pdp constant temperature, dp.
我们已经知道了这个，所以我们现在,可以写出H的微分式：dH等于，加上恒温时的偏H偏。
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So we have dH/dT keeping pressure constant, is du/dT keeping pressure constant.
等于偏U偏T，p恒定加上，偏pv偏T，p恒定。
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SdT So dG is dH minus T dS minus S dT.
所以dG等于dH减去TdS再减去。
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We already did that. OK, dH/dT constant pressure is Cp. That was easy one.
我们已经做过这个计算了，好的，在恒压,状态下的偏H偏T就是Cp，这个很简单。
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dT That means that dH is also equal to dH/dT, constant pressure dT. All right, so now I've T ot more dH/dT under constant pressure.
也等于偏H偏T恒压乘以，现在我已经得到了在恒压,状态下的偏H偏。
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OK, so now we have the other one, p dH/dp constant temperature.
好的，现在我们来研究另一个量，在恒温条件下的偏H偏。
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T Remember, we're trying to get delta H, p we're trying to get dH/dT constant pressure and dH/dp constant temperature. OK, these are the two things were trying to get here.
想要得到在恒压状态下的偏H偏，和在恒温状态下的偏H偏,好的，这是两个我们，在这里想要得到的东西。
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So we could write that criterion as dH less than zero.
我们可以认为dH小于零即为我们的判据。
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OK, in a few weeks, you're going to find out that we can calculate dH/dp from this equation of state, and you're going to find p out that dH/dp from that equation of state b-a/RT is proportional to b minus a over RT.
好，在接下来几个星期里,你们将知道从这个状态方程,可以计算出偏H偏p，并且你们会发现,从这个状态方程得到的偏H偏,正比于。
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