That was a constant enthalpy change.

这个过程是一个自由焓不变的过程。

麻省理工公开课 - 热力学与动力学课程节选

You just change volume to pressure and basically you're looking at enthalpy under a constant -- anything that's done at a constant volume path with energy, there's the same thing happening under constant pressure path for enthalpy.

可以看到这就是把体积换成了压强,一般我们都是在一种恒定状态下,考虑焓的，任何在恒容条件下,能伴随能量变化的东西，也在恒压条件下伴随焓同样地变化,所以你可以经常。

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And if I do that then I can find out the change in enthalpy of this reaction. It's just going to be the heat of formation of these three moles of water, minus the heat of formation of the iron oxide. OK.

我就能得到这个,反应的焓的变化,它就是三摩尔水,的生成热，减去氧化铁的,生成热，好。

麻省理工公开课 - 热力学与动力学课程节选

pV So there is an arbitrary set point that needs to be defined, right? Because what you actually measure in the lab are changes in enthalpy, just like what you measure when you look at energy change of some sort, you measure the change in energy, right.

焓也是一样，焓是U加,所以需要定义一个任意的设定值,对吧？因为实际上你在实验室里,测得的是焓的改变,就像你在研究某种能量变化时，所测量的那样，你测量的是能量的改变，对吧。

麻省理工公开课 - 热力学与动力学课程节选