可汗学院公开课：基础化学81104集英中字幕2.doc

目 录 [第81集] 81.卡诺热机的效率 2 [第82集] 82.卡诺热机的效率2——逆卡诺热机 10 [第83集] 83.卡诺热机的效率——卡诺热机效率最高 19 [第84集] 84.焓 26 [第85集] 85.生成热 35 [第86集] 86.盖斯定律与反应焓变 43 [第87集] 87.吉布斯自由能变与自发性 51 [第88集] 88.吉布斯自由能举例 62 [第89集] 89.吉布斯自由能变与自发性的推导 68 [第90集] 90.一个诱人但是错误的ΔG与自发性的证明 76 [第91集] 91.化学计量学例题1 80 [第92集] 92.化学计量学例题2 86 [第93集] 93.限制性反应物例题 95 [第94集] 94.化学计量法求实验式与分子式 104 [第95集] 95.求反应物实验式 112 [第96集] 96.溶液中的化学计量 120 [第97集] 97.溶液化学计量例题 125 [第98集] 98.由质量分数求实验式与分子式 130 [第99集] 99.强碱滴定二元酸 135 [第100集] 100.分光光度法 141 [第101集] 101.分光光度法例题 148 [第102集] 102.盖斯定律例题 153 [第103集] 103.饱和蒸气压例题 160 [第104集] 104.相变例题 167 [第81集] 81.卡诺热机的效率 E081 Im now going to introduce you to the notion of the efficiency of an engine. And its represented by the Greek letter eta. Even though it sounds like an e, it looks like a kind of funny-looking n. So Greek letter eta, this is efficiency. And efficiency as applies to engines is kind of similar to the way we use the word in our everyday life. If I said, how efficient are you with your time, I care about, what are you doing with that hour that I gave you? Or if I said, how efficient are you with your money, Id say, how much were you able to buy with that $100 I gave you? So efficiency with an engine is the same thing. What were you able to do with the stuff that I gave you? So in the engine world, we define efficiency to be, the work you did with the energy that I gave you to do the work, essentially. And in our Carnot world, up here, this is all the stuff Id done before, what was the energy that I had given you? Well, the energy that Id given you was the energy that came from this first reservoir up here. Remember, when we were moving the pebbles from A to B, we were moving the pebbles to keep it as a quasistatic process, so that we can go back, if we had to, and so that the system stayed in equilibrium the whole time. If we didnt have this reservoir here, the temperature would have gone down, because were expanding the volume, and all of th