You could run the reaction, take solid iron gaseous oxygen, form iron oxide, measure the heat of formation of it, tabulate it.

你可以进行一个反应,用固态铁和氧气生成氧化铁，测量它的生成热，列成表格。

麻省理工公开课 - 热力学与动力学课程节选

But this is a compound, right, it has some non-zero heat of formation from the elements. So is water, right?

但这是种化合物，对吧？,它具有非零的生成热,水也是一样，对吧？

麻省理工公开课 - 热力学与动力学课程节选

So we're just subtracting, in effect, zero, right, from the enthalpy of the product, but of course it's important have that established because the heat of formation is something you could measure, right?

所以从效果上说，我们只是，从生成物的焓中减去了零，但，是确立这一点很重要,因为生成热是,你能测量的东西，对吧？

麻省理工公开课 - 热力学与动力学课程节选

Hf What's my heat of formation? Delta Hf.

生成热是什么？△

麻省理工公开课 - 热力学与动力学课程节选

This is the negative heat of formation, right?

这里是负的生成热，对吧？

麻省理工公开课 - 热力学与动力学课程节选

We can tabulate them. We can know them, and then when we have reactions that inter-convert different compounds, we can calculate the heat of reaction is just the difference between the heat of formation of the reactants, and the heat of formation of the products, right.

种化合物的生成热，可以把它们列成表,可以认知它们，而当我们要处理，在不同化合物间转变的反应时,我们只要计算反应物和,生成物的生成热之间的不同,就能计算出反应热。

麻省理工公开课 - 热力学与动力学课程节选

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

So here, I'm going to have delta H, is just the sum for all the products of delta heat of formation right? Here I'm going to put together all the products. So this is a positive heat of formation.

所以这里△H就是所有生成物的,生成热的和,对吧？这里,我要把元素组合成所有这些,生成物，所以这里是正的生成热。

麻省理工公开课 - 热力学与动力学课程节选