作者frankwu0507 (....)
看板Chemistry
標題[問題] 有機問題
時間Tue Sep 13 18:07:58 2011
Consider the three-step mechanism for the reaction of A through intermediates
B and C to produce D shown below.
A → B Ea = 15 kcal/mol, ΔH° = 13 kcal/mol
B → C Ea = 10 kcal/mol, ΔH° = -6 kcal/mol
C → D Ea = 2 kcal/mol, ΔH° = -20 kcal/mol
Which of the three steps is rate-limiting?
A) The reaction of A to B.
B) The reaction of B to C.
C) The reaction of C to D.
D) All three steps occur at the same rate; there is no rate-limiting step.
E) The most exothermic step is rate-limiting.
我認為答案是B 因為B → C有最高的能量
可是答案是A
想請問一下是答案有問題 還是我有地方想錯了
謝謝!!!
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※ 編輯: frankwu0507 來自: 114.40.145.86 (09/13 18:21)
1F：推 alturiak:看Ea 決定反應速率 09/13 18:51
2F：→ frankwu0507:基本上看Ea似乎是不正確的 例如radical reaction中的 09/13 18:53
3F：→ frankwu0507:初始反應Ea是全連鎖反應中最大的，但反應決定步驟卻是 09/13 18:54
4F：→ frankwu0507:first propagation 09/13 18:54
5F：→ kop5236:我也以為是A 如果考慮FREE RADICAL就不用玩了吧= = 09/14 09:19
6F：→ frankwu0507:In general, the rate-limiting step is the step 09/16 00:51
7F：→ frankwu0507:with the highest-energy transition state. 09/16 00:51
8F：→ frankwu0507:-- from wade 09/16 00:51