[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.41,0:00:01.67,Default,,0000,0000,0000,,有個反應是
Dialogue: 0,0:00:01.69,0:00:03.42,Default,,0000,0000,0000,,1mol的甲烷
Dialogue: 0,0:00:03.43,0:00:05.59,Default,,0000,0000,0000,,和2mol的氧氣反應
Dialogue: 0,0:00:05.61,0:00:08.22,Default,,0000,0000,0000,,會生成1mol的二氧化碳
Dialogue: 0,0:00:08.24,0:00:09.43,Default,,0000,0000,0000,,和2mol的水
Dialogue: 0,0:00:09.44,0:00:11.63,Default,,0000,0000,0000,,這集裏 我們想判斷
Dialogue: 0,0:00:11.65,0:00:14.94,Default,,0000,0000,0000,,這個反應是不是自發的
Dialogue: 0,0:00:14.96,0:00:16.20,Default,,0000,0000,0000,,上次我們已經學過
Dialogue: 0,0:00:16.21,0:00:17.75,Default,,0000,0000,0000,,怎麽判斷自發性啦
Dialogue: 0,0:00:17.76,0:00:19.70,Default,,0000,0000,0000,,這時候就要利用吉布斯自由能
Dialogue: 0,0:00:19.71,0:00:21.33,Default,,0000,0000,0000,,或吉布斯自由能變啦
Dialogue: 0,0:00:21.34,0:00:23.52,Default,,0000,0000,0000,,而吉布斯自由能變ΔG
Dialogue: 0,0:00:23.53,0:00:28.14,Default,,0000,0000,0000,,等於反應的焓變ΔH
Dialogue: 0,0:00:28.16,0:00:30.70,Default,,0000,0000,0000,,減去反應的溫度T
Dialogue: 0,0:00:30.71,0:00:32.82,Default,,0000,0000,0000,,乘以熵變ΔS
Dialogue: 0,0:00:32.84,0:00:35.01,Default,,0000,0000,0000,,如果ΔG<0
Dialogue: 0,0:00:35.03,0:00:39.40,Default,,0000,0000,0000,,那反應就是自發的了
Dialogue: 0,0:00:39.41,0:00:41.86,Default,,0000,0000,0000,,我先給大夥開個好頭
Dialogue: 0,0:00:41.88,0:00:44.04,Default,,0000,0000,0000,,我剛剛已經把
Dialogue: 0,0:00:44.06,0:00:46.08,Default,,0000,0000,0000,,反應的焓變算出來了
Dialogue: 0,0:00:46.09,0:00:47.46,Default,,0000,0000,0000,,就在這裡呢
Dialogue: 0,0:00:47.48,0:00:48.44,Default,,0000,0000,0000,,大家都知道怎麽求ΔH了吧
Dialogue: 0,0:00:48.45,0:00:50.17,Default,,0000,0000,0000,,幾集前我們講過的
Dialogue: 0,0:00:50.18,0:00:52.36,Default,,0000,0000,0000,,先查出來每個產物的
Dialogue: 0,0:00:52.38,0:00:54.48,Default,,0000,0000,0000,,生成熱
Dialogue: 0,0:00:54.49,0:00:56.65,Default,,0000,0000,0000,,例如水 你要把生成熱乘以2
Dialogue: 0,0:00:56.67,0:00:58.17,Default,,0000,0000,0000,,因爲反應生成了2mol的水
Dialogue: 0,0:00:58.18,0:01:00.71,Default,,0000,0000,0000,,這樣就有了產物的生成熱之和
Dialogue: 0,0:01:00.73,0:01:02.07,Default,,0000,0000,0000,,然後再減去
Dialogue: 0,0:01:02.09,0:01:03.94,Default,,0000,0000,0000,,反應物的生成熱之和
Dialogue: 0,0:01:03.96,0:01:07.10,Default,,0000,0000,0000,,當然啦 O2的生成熱是0
Dialogue: 0,0:01:07.11,0:01:08.51,Default,,0000,0000,0000,,所以式子裏面沒有這項
Dialogue: 0,0:01:08.52,0:01:11.91,Default,,0000,0000,0000,,算出來就是 -890.3kJ
Dialogue: 0,0:01:11.93,0:01:12.06,Default,,0000,0000,0000,,好啦
Dialogue: 0,0:01:12.07,0:01:14.95,Default,,0000,0000,0000,,這就說明 反應是放熱的
Dialogue: 0,0:01:14.97,0:01:18.38,Default,,0000,0000,0000,,方程式這邊的能量少於…
Dialogue: 0,0:01:18.40,0:01:19.63,Default,,0000,0000,0000,,你也可以這樣想的…
Dialogue: 0,0:01:19.65,0:01:20.36,Default,,0000,0000,0000,,比那邊的能量小
Dialogue: 0,0:01:20.37,0:01:22.65,Default,,0000,0000,0000,,所以必須釋放能量才行
Dialogue: 0,0:01:22.67,0:01:25.43,Default,,0000,0000,0000,,可以在這裡寫 +e e代表能量
Dialogue: 0,0:01:25.44,0:01:25.92,Default,,0000,0000,0000,,我寫上
Dialogue: 0,0:01:25.93,0:01:28.08,Default,,0000,0000,0000,,加上釋放出來的能量
Dialogue: 0,0:01:28.10,0:01:29.72,Default,,0000,0000,0000,,這就是反應放熱的原因啦
Dialogue: 0,0:01:29.74,0:01:31.96,Default,,0000,0000,0000,,但是問題是 反應是不是自發的呢？
Dialogue: 0,0:01:31.97,0:01:33.55,Default,,0000,0000,0000,,想要判斷反應的自發性
Dialogue: 0,0:01:33.57,0:01:39.24,Default,,0000,0000,0000,,首先要算出ΔS
Dialogue: 0,0:01:39.26,0:01:41.38,Default,,0000,0000,0000,,爲了計算ΔS的值呢
Dialogue: 0,0:01:41.40,0:01:43.19,Default,,0000,0000,0000,,我提前就查好了
Dialogue: 0,0:01:43.21,0:01:48.14,Default,,0000,0000,0000,,這裡每種分子的標準莫耳熵
Dialogue: 0,0:01:48.16,0:01:49.61,Default,,0000,0000,0000,,比如說 標準…
Dialogue: 0,0:01:49.63,0:01:51.41,Default,,0000,0000,0000,,我換個顏色表示
Dialogue: 0,0:01:51.42,0:01:53.36,Default,,0000,0000,0000,,標準
Dialogue: 0,0:01:53.38,0:01:56.79,Default,,0000,0000,0000,,小小講點拓展 這裡沒有Δ
Dialogue: 0,0:01:56.80,0:02:00.51,Default,,0000,0000,0000,,我擦了吧 還能補救
Dialogue: 0,0:02:00.53,0:02:02.85,Default,,0000,0000,0000,,標準
Dialogue: 0,0:02:02.87,0:02:05.24,Default,,0000,0000,0000,,這裡畫個圈裏面帶個橫表示
Dialogue: 0,0:02:05.26,0:02:07.40,Default,,0000,0000,0000,,標準莫耳熵Sm
Dialogue: 0,0:02:07.41,0:02:10.85,Default,,0000,0000,0000,,“標準”指的是在298°K下
Dialogue: 0,0:02:10.86,0:02:12.66,Default,,0000,0000,0000,,實際不應該說“度克耳文”
Dialogue: 0,0:02:12.68,0:02:14.59,Default,,0000,0000,0000,,就是298K
Dialogue: 0,0:02:14.60,0:02:16.42,Default,,0000,0000,0000,,用克耳文K的時候
Dialogue: 0,0:02:16.44,0:02:17.45,Default,,0000,0000,0000,,不用說度°
Dialogue: 0,0:02:17.46,0:02:19.24,Default,,0000,0000,0000,,所以反應溫度是289K
Dialogue: 0,0:02:19.26,0:02:20.65,Default,,0000,0000,0000,,也就是25°C
Dialogue: 0,0:02:20.66,0:02:22.10,Default,,0000,0000,0000,,相當於室溫
Dialogue: 0,0:02:22.11,0:02:24.30,Default,,0000,0000,0000,,所以用289K作標準狀態
Dialogue: 0,0:02:24.32,0:02:29.24,Default,,0000,0000,0000,,所以室溫下 甲烷的標準莫耳熵
Dialogue: 0,0:02:29.26,0:02:31.03,Default,,0000,0000,0000,,就等於這個數
Dialogue: 0,0:02:37.81,0:02:40.38,Default,,0000,0000,0000,,所以如果有1mol的甲烷
Dialogue: 0,0:02:40.40,0:02:43.89,Default,,0000,0000,0000,,就有186J/K的熵
Dialogue: 0,0:02:43.90,0:02:46.13,Default,,0000,0000,0000,,如果有2mol的甲烷 就乘以2
Dialogue: 0,0:02:46.14,0:02:48.42,Default,,0000,0000,0000,,如果有3mol 就乘以3
Dialogue: 0,0:02:48.43,0:02:53.46,Default,,0000,0000,0000,,所以這個反應的總熵變
Dialogue: 0,0:02:53.47,0:02:58.02,Default,,0000,0000,0000,,就是產物標準熵之和
Dialogue: 0,0:02:58.04,0:03:00.69,Default,,0000,0000,0000,,減去反應物標準熵之和
Dialogue: 0,0:03:00.70,0:03:02.55,Default,,0000,0000,0000,,就跟算ΔHr差不多
Dialogue: 0,0:03:02.56,0:03:09.76,Default,,0000,0000,0000,,所以熵變就等於213.6 加上…
Dialogue: 0,0:03:09.77,0:03:12.39,Default,,0000,0000,0000,,產物裏有2mol的水
Dialogue: 0,0:03:12.40,0:03:15.92,Default,,0000,0000,0000,,所以就是加上2乘以…
Dialogue: 0,0:03:15.94,0:03:17.85,Default,,0000,0000,0000,,就取70好了
Dialogue: 0,0:03:17.86,0:03:19.80,Default,,0000,0000,0000,,69.9 約等於70
Dialogue: 0,0:03:19.82,0:03:21.91,Default,,0000,0000,0000,,加上2×70
Dialogue: 0,0:03:21.92,0:03:23.79,Default,,0000,0000,0000,,然後再減去
Dialogue: 0,0:03:23.80,0:03:26.11,Default,,0000,0000,0000,,反應物的熵之和
Dialogue: 0,0:03:26.12,0:03:28.91,Default,,0000,0000,0000,,也就是方程式這邊的這些
Dialogue: 0,0:03:28.92,0:03:31.77,Default,,0000,0000,0000,,1molCH4的熵
Dialogue: 0,0:03:31.78,0:03:42.86,Default,,0000,0000,0000,,等於186 加上2×205
Dialogue: 0,0:03:42.88,0:03:44.25,Default,,0000,0000,0000,,大概心算一下
Dialogue: 0,0:03:44.27,0:03:45.67,Default,,0000,0000,0000,,這個數非常接近這個數
Dialogue: 0,0:03:45.69,0:03:48.02,Default,,0000,0000,0000,,但是這個數比這個數大得多
Dialogue: 0,0:03:48.04,0:03:50.33,Default,,0000,0000,0000,,液態水的熵…
Dialogue: 0,0:03:50.35,0:03:51.99,Default,,0000,0000,0000,,這是液態水的熵
Dialogue: 0,0:03:52.00,0:03:54.65,Default,,0000,0000,0000,,它的熵遠遠少於氧氣的熵
Dialogue: 0,0:03:54.67,0:03:55.76,Default,,0000,0000,0000,,這很合理呀
Dialogue: 0,0:03:55.77,0:03:58.57,Default,,0000,0000,0000,,因爲液態水的微觀狀態數比氧氣少得多
Dialogue: 0,0:03:58.58,0:04:02.37,Default,,0000,0000,0000,,液態水都沈在容器底了
Dialogue: 0,0:04:02.39,0:04:03.04,Default,,0000,0000,0000,,氣體就不同
Dialogue: 0,0:04:03.05,0:04:04.67,Default,,0000,0000,0000,,氣體能膨脹 隨空間變換形狀
Dialogue: 0,0:04:04.69,0:04:06.03,Default,,0000,0000,0000,,所以理所當然 氣體的熵
Dialogue: 0,0:04:06.05,0:04:08.15,Default,,0000,0000,0000,,比液體的熵大的多
Dialogue: 0,0:04:08.17,0:04:09.26,Default,,0000,0000,0000,,簡單心算
Dialogue: 0,0:04:09.27,0:04:12.28,Default,,0000,0000,0000,,就已經能看出來產物的熵
Dialogue: 0,0:04:12.30,0:04:14.02,Default,,0000,0000,0000,,比反應物的熵小
Dialogue: 0,0:04:14.03,0:04:15.46,Default,,0000,0000,0000,,所以熵變應該是負的
Dialogue: 0,0:04:15.48,0:04:19.43,Default,,0000,0000,0000,,不過我們還是確認一下
Dialogue: 0,0:04:19.44,0:04:28.54,Default,,0000,0000,0000,,這個是213.6加上…
Dialogue: 0,0:04:28.56,0:04:30.75,Default,,0000,0000,0000,,是加上140 對嘛？
Dialogue: 0,0:04:30.76,0:04:31.38,Default,,0000,0000,0000,,是2×70
Dialogue: 0,0:04:31.39,0:04:35.55,Default,,0000,0000,0000,,加上140 就等於353.6
Dialogue: 0,0:04:35.56,0:04:39.90,Default,,0000,0000,0000,,這部分等於353.6
Dialogue: 0,0:04:39.91,0:04:43.58,Default,,0000,0000,0000,,然後從這裡減去…
Dialogue: 0,0:04:43.59,0:04:52.66,Default,,0000,0000,0000,,所以186 加上2×205
Dialogue: 0,0:04:52.67,0:04:54.43,Default,,0000,0000,0000,,就等於596
Dialogue: 0,0:04:54.44,0:04:57.17,Default,,0000,0000,0000,,所以就是減去596
Dialogue: 0,0:04:57.19,0:04:58.60,Default,,0000,0000,0000,,最後等於什麽？
Dialogue: 0,0:04:58.62,0:05:06.43,Default,,0000,0000,0000,,-596 加上353.6
Dialogue: 0,0:05:06.44,0:05:10.52,Default,,0000,0000,0000,,等於-242.4
Dialogue: 0,0:05:10.53,0:05:17.61,Default,,0000,0000,0000,,所以它就等於-242.4J/K
Dialogue: 0,0:05:17.63,0:05:21.20,Default,,0000,0000,0000,,這就是ΔS 負的
Dialogue: 0,0:05:21.22,0:05:24.06,Default,,0000,0000,0000,,所以係統的熵減少了這麽多
Dialogue: 0,0:05:24.08,0:05:25.98,Default,,0000,0000,0000,,你可能對熵的單位大小沒有概念
Dialogue: 0,0:05:25.99,0:05:28.95,Default,,0000,0000,0000,,不過只要知道是某個大小就可以
Dialogue: 0,0:05:28.96,0:05:29.62,Default,,0000,0000,0000,,但是你可以說 喏
Dialogue: 0,0:05:29.63,0:05:30.83,Default,,0000,0000,0000,,反應之後係統更有序啦
Dialogue: 0,0:05:30.84,0:05:32.76,Default,,0000,0000,0000,,這很合理 因爲開始是一大堆氣體
Dialogue: 0,0:05:32.77,0:05:35.35,Default,,0000,0000,0000,,開始是3個單獨的分子
Dialogue: 0,0:05:35.36,0:05:38.30,Default,,0000,0000,0000,,有1個甲烷 還有2個氧氣
Dialogue: 0,0:05:38.31,0:05:40.08,Default,,0000,0000,0000,,後來還是3個分子
Dialogue: 0,0:05:40.10,0:05:42.39,Default,,0000,0000,0000,,但是這個水是液態的
Dialogue: 0,0:05:42.40,0:05:45.52,Default,,0000,0000,0000,,所以 反應後熵減小是有道理的
Dialogue: 0,0:05:45.53,0:05:48.57,Default,,0000,0000,0000,,尤其液態物質 它的微觀狀態數很少
Dialogue: 0,0:05:48.59,0:05:49.43,Default,,0000,0000,0000,,我們來判斷一下
Dialogue: 0,0:05:49.45,0:05:51.21,Default,,0000,0000,0000,,這個反應是不是自發的
Dialogue: 0,0:05:51.22,0:05:57.51,Default,,0000,0000,0000,,ΔG等於ΔH…
Dialogue: 0,0:05:57.53,0:06:00.88,Default,,0000,0000,0000,,反應放熱 所以就是-890
Dialogue: 0,0:06:00.90,0:06:02.54,Default,,0000,0000,0000,,我把小數省略掉了
Dialogue: 0,0:06:02.55,0:06:03.99,Default,,0000,0000,0000,,我們不用那麽精確
Dialogue: 0,0:06:04.01,0:06:05.93,Default,,0000,0000,0000,,減去溫度
Dialogue: 0,0:06:05.95,0:06:08.28,Default,,0000,0000,0000,,假設反應是在室溫下進行的
Dialogue: 0,0:06:08.29,0:06:10.21,Default,,0000,0000,0000,,所以溫度是298°K
Dialogue: 0,0:06:10.23,0:06:13.39,Default,,0000,0000,0000,,就是… 我應該說“298K”
Dialogue: 0,0:06:13.40,0:06:14.42,Default,,0000,0000,0000,,我要改掉壞習慣
Dialogue: 0,0:06:14.43,0:06:15.91,Default,,0000,0000,0000,,在用K表示溫度的時候 不說“°”
Dialogue: 0,0:06:15.93,0:06:18.71,Default,,0000,0000,0000,,298K 也就是25°C
Dialogue: 0,0:06:18.73,0:06:22.10,Default,,0000,0000,0000,,再乘以熵變
Dialogue: 0,0:06:22.12,0:06:24.92,Default,,0000,0000,0000,,這項是負的
Dialogue: 0,0:06:24.94,0:06:27.46,Default,,0000,0000,0000,,你可能會說 好的 是-242
Dialogue: 0,0:06:27.47,0:06:28.54,Default,,0000,0000,0000,,直接把這個數放進去
Dialogue: 0,0:06:28.55,0:06:30.36,Default,,0000,0000,0000,,但是你要非常非常非常的小心
Dialogue: 0,0:06:30.37,0:06:33.04,Default,,0000,0000,0000,,它的單位是千焦kJ
Dialogue: 0,0:06:33.05,0:06:34.94,Default,,0000,0000,0000,,可是它的單位是焦耳J
Dialogue: 0,0:06:34.96,0:06:37.63,Default,,0000,0000,0000,,所以如果都以千焦做單位的話
Dialogue: 0,0:06:37.64,0:06:38.87,Default,,0000,0000,0000,,因爲前面寫了kJ
Dialogue: 0,0:06:38.89,0:06:40.48,Default,,0000,0000,0000,,我們把這個也換算成千焦吧
Dialogue: 0,0:06:40.50,0:06:46.99,Default,,0000,0000,0000,,所以它就是0.242kJ/K
Dialogue: 0,0:06:47.00,0:06:48.10,Default,,0000,0000,0000,,前面放個小數點
Dialogue: 0,0:06:48.11,0:06:50.11,Default,,0000,0000,0000,,這裡的0.45擦掉
Dialogue: 0,0:06:50.12,0:06:51.89,Default,,0000,0000,0000,,單位是kJ/k
Dialogue: 0,0:06:51.91,0:06:55.51,Default,,0000,0000,0000,,所以吉布斯自由能變
Dialogue: 0,0:06:55.53,0:07:00.25,Default,,0000,0000,0000,,就是-890kJ 減去298…
Dialogue: 0,0:07:00.26,0:07:02.66,Default,,0000,0000,0000,,負負得正
Dialogue: 0,0:07:02.69,0:07:03.88,Default,,0000,0000,0000,,完全合理
Dialogue: 0,0:07:03.89,0:07:05.65,Default,,0000,0000,0000,,因爲熵的這項
Dialogue: 0,0:07:05.66,0:07:08.39,Default,,0000,0000,0000,,會使吉布斯自由能變得更正
Dialogue: 0,0:07:08.41,0:07:09.41,Default,,0000,0000,0000,,因爲
Dialogue: 0,0:07:09.43,0:07:12.08,Default,,0000,0000,0000,,我們想讓ΔG<0
Dialogue: 0,0:07:12.09,0:07:14.07,Default,,0000,0000,0000,,但是ΔS>0會降低自發性
Dialogue: 0,0:07:14.09,0:07:18.84,Default,,0000,0000,0000,,現在我們來看這項能不能抵消ΔH
Dialogue: 0,0:07:18.85,0:07:20.59,Default,,0000,0000,0000,,也就是放熱的影響
Dialogue: 0,0:07:20.61,0:07:21.67,Default,,0000,0000,0000,,目測好像是不行
Dialogue: 0,0:07:21.67,0:07:23.71,Default,,0000,0000,0000,,因爲一個小數乘以它
Dialogue: 0,0:07:23.73,0:07:25.13,Default,,0000,0000,0000,,得到的數肯定更小
Dialogue: 0,0:07:25.15,0:07:26.72,Default,,0000,0000,0000,,我們算算看
Dialogue: 0,0:07:26.73,0:07:31.04,Default,,0000,0000,0000,,所以除以 1,2,3 3個0
Dialogue: 0,0:07:31.05,0:07:34.32,Default,,0000,0000,0000,,係統的熵變
Dialogue: 0,0:07:34.33,0:07:37.81,Default,,0000,0000,0000,,乘以298 這是係統的溫度
Dialogue: 0,0:07:37.82,0:07:40.16,Default,,0000,0000,0000,,等於-72
Dialogue: 0,0:07:40.17,0:07:42.61,Default,,0000,0000,0000,,所以這項就等於…
Dialogue: 0,0:07:42.63,0:07:43.79,Default,,0000,0000,0000,,因爲前面還有個減號…
Dialogue: 0,0:07:43.81,0:07:46.86,Default,,0000,0000,0000,,所以就是加上72.2
Dialogue: 0,0:07:46.87,0:07:50.01,Default,,0000,0000,0000,,所以這就是標準溫度下的熵的項
Dialogue: 0,0:07:50.03,0:07:51.36,Default,,0000,0000,0000,,最後就等於它咯
Dialogue: 0,0:07:51.37,0:07:53.04,Default,,0000,0000,0000,,而這是焓項
Dialogue: 0,0:07:53.05,0:07:54.16,Default,,0000,0000,0000,,這樣我們就能看出來
Dialogue: 0,0:07:54.18,0:07:57.02,Default,,0000,0000,0000,,焓變的絕對值
Dialogue: 0,0:07:57.04,0:07:59.04,Default,,0000,0000,0000,,比T×ΔS的絕對值
Dialogue: 0,0:07:59.05,0:08:00.37,Default,,0000,0000,0000,,大得多
Dialogue: 0,0:08:00.38,0:08:04.53,Default,,0000,0000,0000,,所以這項壓倒性勝利了
Dialogue: 0,0:08:04.55,0:08:06.91,Default,,0000,0000,0000,,雖然反應是個熵減的反應
Dialogue: 0,0:08:06.92,0:08:09.11,Default,,0000,0000,0000,,但是反應放出的熱量太多了
Dialogue: 0,0:08:09.13,0:08:10.93,Default,,0000,0000,0000,,所以反應仍然是自發
Dialogue: 0,0:08:10.95,0:08:12.89,Default,,0000,0000,0000,,這個數顯然少於0
Dialogue: 0,0:08:12.91,0:08:17.34,Default,,0000,0000,0000,,所以這是個自發反應
Dialogue: 0,0:08:17.35,0:08:19.40,Default,,0000,0000,0000,,如你所見 這些吉布斯自由能的問題
Dialogue: 0,0:08:19.42,0:08:20.71,Default,,0000,0000,0000,,其實沒那麽難
Dialogue: 0,0:08:20.73,0:08:23.57,Default,,0000,0000,0000,,只要知道這幾項的值就行啦
Dialogue: 0,0:08:23.58,0:08:27.13,Default,,0000,0000,0000,,這幾項的值要麽直接給出
Dialogue: 0,0:08:27.15,0:08:27.97,Default,,0000,0000,0000,,比如ΔH
Dialogue: 0,0:08:27.99,0:08:29.83,Default,,0000,0000,0000,,不過我們也知道怎麽求出來
Dialogue: 0,0:08:29.85,0:08:31.24,Default,,0000,0000,0000,,只要查到產物的
Dialogue: 0,0:08:31.25,0:08:32.54,Default,,0000,0000,0000,,生成熱
Dialogue: 0,0:08:32.55,0:08:34.64,Default,,0000,0000,0000,,再減去反應物的生成熱
Dialogue: 0,0:08:34.65,0:08:37.77,Default,,0000,0000,0000,,當然還要各自乘以相應的化學計量數
Dialogue: 0,0:08:37.78,0:08:40.17,Default,,0000,0000,0000,,然後 用同樣的方法
Dialogue: 0,0:08:40.18,0:08:41.01,Default,,0000,0000,0000,,算出熵變
Dialogue: 0,0:08:41.03,0:08:43.65,Default,,0000,0000,0000,,查到每種產物的標準莫耳熵
Dialogue: 0,0:08:43.67,0:08:46.00,Default,,0000,0000,0000,,分別乘以相應的化學計量數
Dialogue: 0,0:08:46.02,0:08:47.81,Default,,0000,0000,0000,,再減去反應物的總熵
Dialogue: 0,0:08:47.82,0:08:49.97,Default,,0000,0000,0000,,然後把數代入這個式子中
Dialogue: 0,0:08:49.99,0:08:51.98,Default,,0000,0000,0000,,最後就得到了吉布斯自由能變
Dialogue: 0,0:08:51.99,0:08:54.56,Default,,0000,0000,0000,,這個例子裏 ΔG是負的
Dialogue: 0,0:08:54.57,0:08:56.17,Default,,0000,0000,0000,,現在 大家可以想象一下
Dialogue: 0,0:08:56.19,0:08:57.78,Default,,0000,0000,0000,,溫度極高的情況
Dialogue: 0,0:08:57.80,0:09:00.20,Default,,0000,0000,0000,,比如太陽表面之類的
Dialogue: 0,0:09:00.22,0:09:04.00,Default,,0000,0000,0000,,溫度就不是298K啦
Dialogue: 0,0:09:04.01,0:09:07.98,Default,,0000,0000,0000,,溫度一下子變成了2000K或者4000K
Dialogue: 0,0:09:08.00,0:09:09.92,Default,,0000,0000,0000,,這時候就有意思啦
Dialogue: 0,0:09:09.94,0:09:11.43,Default,,0000,0000,0000,,比如說
Dialogue: 0,0:09:11.45,0:09:15.66,Default,,0000,0000,0000,,反應溫度是40000K
Dialogue: 0,0:09:15.67,0:09:17.52,Default,,0000,0000,0000,,那麽熵這一項
Dialogue: 0,0:09:17.54,0:09:19.87,Default,,0000,0000,0000,,也就是熵減 影響就可大啦
Dialogue: 0,0:09:19.89,0:09:22.30,Default,,0000,0000,0000,,所以正的這一項
Dialogue: 0,0:09:22.31,0:09:23.19,Default,,0000,0000,0000,,就抵消這一項
Dialogue: 0,0:09:23.21,0:09:25.65,Default,,0000,0000,0000,,所以在超高溫下
Dialogue: 0,0:09:25.67,0:09:28.01,Default,,0000,0000,0000,,反應可能就無法自發進行啦
Dialogue: 0,0:09:28.02,0:09:29.11,Default,,0000,0000,0000,,換個角度
Dialogue: 0,0:09:29.12,0:09:34.23,Default,,0000,0000,0000,,一個反應放出熱量…
Dialogue: 0,0:09:34.24,0:09:36.30,Default,,0000,0000,0000,,周圍溫度已經非常高
Dialogue: 0,0:09:36.31,0:09:38.18,Default,,0000,0000,0000,,分子的動能已經很大了的時候
Dialogue: 0,0:09:38.19,0:09:40.02,Default,,0000,0000,0000,,放出的熱量就沒什麽影響了
Dialogue: 0,0:09:40.04,0:09:41.46,Default,,0000,0000,0000,,如果周圍溫度足夠高
Dialogue: 0,0:09:41.48,0:09:43.89,Default,,0000,0000,0000,,這個反應就不是自發的了
Dialogue: 0,0:09:43.91,0:09:47.06,Default,,0000,0000,0000,,因爲熵項會把焓抵消掉
Dialogue: 0,0:09:47.08,0:09:47.50,Default,,0000,0000,0000,,好啦
Dialogue: 0,0:09:47.52,0:09:49.02,Default,,0000,0000,0000,,我只是想帶大家算一次
Dialogue: 0,0:09:49.04,0:09:51.35,Default,,0000,0000,0000,,就是想讓大家知道 這沒那麽難
Dialogue: 0,0:09:51.37,0:09:53.01,Default,,0000,0000,0000,,這些數據都可以從網上查到
Dialogue: 0,0:09:53.02,0:09:54.00,Default,,0000,0000,0000,,然後就能判斷出
Dialogue: 0,0:09:54.01,0:09:56.32,Default,,0000,0000,0000,,反應是否可以自發進行了