| English | 意味 |
|---|---|
| intermediate/ˌɪntəˈmiːdɪət/ | 中間体 |
Measure each barrier from its own starting valley
- A two-step profile has reactants at 20, first peak at 80, an intermediate at −20, second peak at 60 and products at 0, all in kJ per mole.
- The forward barriers are 80−20=60 and 60−(−20)=80. The second peak is lower on the page, but the second step has the larger local barrier.
A mountain range, not a single hill
- A one-step reaction has a single hump to climb. A multi-step one has a whole ridge of peaks.
- Each peak is a step; each dip is an intermediate resting. Compare the rise from each starting valley to its following peak.
One hump per step
- A multi-step reaction shows one peak for each elementary step. Between the peaks lie small valleys.
- More steps means more humps.
三段階反応のエネルギープロファイルには何個の山があるか？
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
素反応段階ごとに1個ずつの山があるため、3個の山がある。
Intermediates rest in the dips
- Each valley between two peaks holds an intermediate 中间体. It is more stable than the peaks around it, but not the final product.
- It is briefly formed, then consumed by the next step.
中間体はプロファイル上で...として現れる。
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
中間体は山の間のくぼみに位置する。
The highest barrier rules
- Each activation energy is a difference: transition-state energy minus the energy at the start of that step. In the simplified comparison used here, the larger local barrier identifies the slower step.
- Absolute peak height alone cannot identify that barrier.
Under the simplified barrier comparison, which step is expected to be slower?
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
Compare transition state minus the starting state for each step. Absolute peak height is insufficient.
律速段階は常に最初の段階である。
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
Compare each local forward barrier. Neither first position nor highest absolute peak automatically identifies the slow step.
A two-step diagram has reactants at 20, peaks at 80 and 60, an intermediate at −20 and products at 0, all in $\dfrac{\text{kJ}}{\text{mol}}$.
- Step 1: $E_{a,1}=80-20=60$. Step 2: $E_{a,2}=60-(-20)=80$, in $\dfrac{\text{kJ}}{\text{mol}}$.
- The lower second peak has the larger local barrier, so step 2 is slower under the simplified barrier comparison.
二峰性のエネルギープロファイルを読む
二段階反応のエネルギープロファイル上の各特徴を特定せよ。
遷移状態は山の上にあり、谷の中にない。
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
山は遷移状態、谷は中間体である。
全体的な$\Delta H$は反応物と生成物のエネルギーのみによって決まり、山の高さには依存しない。
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
$\Delta H$は障壁を無視して、生成物から反応物を引いた値である。
The intermediate sits in a valley (a dip), while the transition states sit at the peaks -- do not mix them up. Measure each forward barrier from its own starting valley; do not select a step from the highest absolute peak alone. And the overall $\Delta H$ is still just products minus reactants, ignoring the humps in between.
Carry the reasoning to a new case
- The overall enthalpy change is 0−20=−20 kJ per mole.
- Under the usual simplified barrier comparison, the second step is slower; actual mechanism rates also depend on concentrations and kinetic factors.
Using the profile values, calculate the second forward activation energy in kJ per mole.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Measure from the intermediate at −20 to the second transition state at 60: 60−(−20)=80.
From reactants at 20 to products at 0, calculate the overall enthalpy change in kJ per mole.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Products minus reactants: 0−20=−20. Peak heights do not enter this subtraction.
A multi-step energy profile has one peak per step and an intermediate resting in each valley between them. Compare local activation barriers, measured from each step's starting state; a lower absolute peak may have a larger barrier. The overall $\Delta H$ is still just the difference between the two ends.