Reading an Energy Profile · 阅读能量分布图
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| energy profile/ˈenədʒi ˈprəʊfaɪl/ | 能量图 | néng liàng tú |
| activation energy/ˌæktɪˈveɪʃn ˈenədʒi/ | 活化能 | huó huà néng |
| transition state/trænˈsɪʃn steɪt/ | 过渡态 | guò dù tài |
A hill the reaction must climb
- Every reaction has a hill to get over before it can finish.
- A graph draws that hill as the atoms rearrange.
- Its height tells you how hard the reaction is to start.
- Its two ends tell you whether heat is released or absorbed.
反应必须翻越的山坡
- 每个反应在能完成之前都有一座山坡要翻越。
- 一张图把那座山坡随原子重新排列画出来。
- 它的高度告诉你反应有多难启动。
- 它的两端告诉你是放热还是吸热。
The reaction-coordinate diagram
- An energy profile 能量图 plots energy along the reaction's progress.
- Reactants sit on the left and products on the right.
- A hill rises between them.
反应坐标图
- 能量图把能量沿反应的进程作图。
- 反应物在左边,产物在右边。
- 一座山坡在它们之间升起。
The peak is the barrier
- The peak height above the reactants is the activation energy 活化能.
- At the very top sits the transition state 过渡态.
- A higher peak means a slower reaction.
山峰就是壁垒
- 山峰高出反应物的高度就是活化能。
- 最顶端是过渡态。
- 山峰越高,反应越慢。
The transition state is located at the... · 过渡态位于...
The transition state sits at the very top of the barrier. · 过渡态位于势垒的最顶端。
A higher activation energy makes a reaction slower. · 较高的活化能使反应变慢。
Fewer collisions can clear a taller barrier. · 较少的碰撞能够越过更高的势垒。
Uphill or downhill overall
- If products sit lower than reactants, energy is released (exothermic).
- If products sit higher, energy is absorbed (endothermic).
- The difference between the two ends is $\Delta H$.
整体上坡还是下坡
- 若产物比反应物低,释放能量(放热)。
- 若产物比反应物高,吸收能量(吸热)。
- 两端之间的差就是 $\Delta H$。
Read the energy profile · 读取能量分布图
Find the activation energy, the enthalpy change, and how the reactants climb to the transition state. · 找出活化能、焓变以及反应物如何攀升至过渡态。
Reactants at $40\ \text{kJ}$, products at $25\ \text{kJ}$. The value of $\Delta H$ (in kJ)? · $40\ \text{kJ}$ 处为反应物，$25\ \text{kJ}$ 处为产物。$\Delta H$ 的值（单位为 kJ）是多少？
$\Delta H = 25 - 40 = -15\ \text{kJ}$ (products minus reactants). · $\Delta H = 25 - 40 = -15\ \text{kJ}$（产物减去反应物）。
If the products are lower in energy than the reactants, the reaction is... · 如果产物的能量低于反应物，该反应是...
Lower products mean net energy is released -- exothermic. · 较低的产物意味着净能量释放——即放热反应。
Reactants at $50\ \text{kJ}$, peak at $120\ \text{kJ}$, products at $30\ \text{kJ}$.
- Activation energy $= 120 - 50 = 70\ \text{kJ}$.
- $\Delta H = 30 - 50 = -20\ \text{kJ}$, so it is exothermic.
反应物在 $50\ \text{kJ}$,峰在 $120\ \text{kJ}$,产物在 $30\ \text{kJ}$。
- 活化能 $= 120 - 50 = 70\ \text{kJ}$。
- $\Delta H = 30 - 50 = -20\ \text{kJ}$,所以是放热的。
Reactants at $40\ \text{kJ}$, peak at $100\ \text{kJ}$. The activation energy (in kJ)? · 反应物位于$40\ \text{kJ}$，峰值位于$100\ \text{kJ}$。活化能（单位kJ）是多少？
$E_a = 100 - 40 = 60\ \text{kJ}$ (peak minus reactants). · $E_a = 100 - 40 = 60\ \text{kJ}$（峰值减去反应物）。
Activation energy is measured from the reactants up to the . · 活化能从反应物测量到。
It is the height of the peak above the reactants. · 它是峰值相对于反应物的高度。
Activation energy is measured from the reactants up to the peak, not from zero. $\Delta H$ is the difference between products and reactants (the two ends), independent of the peak height. And a large activation energy makes a reaction slow even if it is strongly exothermic.
活化能是从反应物量到山峰,而不是从零。$\Delta H$ 是产物与反应物(两端)之差,与峰高无关。而且大的活化能会使反应变慢,即使它强烈放热。
An energy profile plots energy along a reaction. The peak above the reactants is the activation energy, with the transition state at the top. Whether products end lower (exothermic) or higher (endothermic) than reactants gives $\Delta H$. Barrier height sets speed; the end difference sets $\Delta H$.
能量图把能量沿反应作图。高出反应物的峰是活化能,顶端是过渡态。产物比反应物低(放热)还是高(吸热)给出 $\Delta H$。壁垒高度决定速度;两端之差决定 $\Delta H$。