18.9 反应令

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  反应顺序

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  How harmful are forest fires?
  ::森林火灾有多有害?

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  Forest fires cause extensive damage when they occur. Both plant and animal life are harmed during these events. The severity of a forest fire depends on how much plant life is available to burn – the more available dry plant material, the more serious the fire and the more rapidly it will spread.
  ::森林火灾一旦发生,就会造成巨大破坏。 在这些事件中,动植物生命都会受到伤害。 森林火灾的严重性取决于有多少植物生命可以燃烧 — — 有多少干燥植物材料,火灾越严重,其蔓延速度就越快。

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  Order of Reaction
  ::反应顺序

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  In the reaction $\begin{align*}A \rightarrow B\end{align*}$ , the rate of the reaction is directly proportional to the of  $\begin{align*}A\end{align*}$ raised to the first power. That is to say, $\begin{align*}[A]=[A]^1\end{align*}$ . A first-order reaction is a reaction in which the rate is proportional to the concentration of only one reactant . As a first-order reaction proceeds, the rate of reaction decreases because the concentration of the reactant decreases (see  Figure  ). The graph of concentration versus time is curved. The $\begin{align*} \left(\frac{\Delta [A]}{\Delta t} \right)\end{align*}$ can be determined graphically by the slope of a tangent to the curve at any point. The rate of the reaction at the time shown with the red triangle is given by:
  ::在AB反应中,反应速率与A升至第一级反应的速率直接成比例。也就是说,[A]=[A]1]。第一级反应是该速率与只有一个反应器的集中度成比例的反应。作为第一级反应的收益,反应速率由于反应器的集中性下降而下降(见图 )。集中度与时间的图是曲线的曲线。([A]}}}(t)可以通过相切值与曲线的任何点的斜坡以图形方式确定。显示红色三角形时的反应速率如下:

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  $$\begin{align*}\text{rate}=-\frac{[A]_{\text{final}}-[A]_{\text{initial}}}{\Delta t}=-\frac{0.35 \text{ M} - 0.63 \text{ M}}{3.0 \text{ s} - 1.0 \text{ s}}=0.14 \text{ M/s}\end{align*}$$
  ::==0.14 m/s

  

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  The rates of some reactions depend on the concentrations of more than one reactant. Consider a reaction in which a molecule of  $\begin{align*}A\end{align*}$ collides with a molecule of  $\begin{align*}B\end{align*}$ to form product $\begin{align*}C\end{align*}$ .
  ::一些反应的速率取决于不止一个反应剂的浓度,考虑A分子与B分子相撞形成产品C的一种反应。

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  $$\begin{align*}A+B \rightarrow C\end{align*}$$
  ::A+B_C+B_C+B_C+B_C+B_C+B_C+B_C+B_C+C+B_C+B_C+C+B_C+B_C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C_C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C+C

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  Doubling the concentration of  $\begin{align*}A\end{align*}$ alone would double the reaction rate. Likewise, doubling the concentration of  $\begin{align*}B\end{align*}$ alone would also double the rate. The rate law must reflect the rate dependence on both reactants.
  ::将A的集中程度翻一番是反应率的两倍。 同样,将B的集中程度翻一番也将是B的两倍。 比率法必须反映对两个反应者的比率依赖性。

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  $$\begin{align*}\text{rate}=k[A][B]\end{align*}$$
  ::速率=k[A][B]

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  This reaction is said to be first order with respect to  $\begin{align*}A\end{align*}$ and first order with respect to $\begin{align*}B\end{align*}$ . Overall, it is a second-order reaction. The rate law and the order of a reaction must be determined experimentally.
  ::据说这种反应对A是第一级,对B是第一级。 总的来说,这是第二级反应,比率法和反应顺序必须实验性地确定。

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  Summary
  ::摘要

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  • A first-order reaction is described.
    ::描述的是第一级反应。

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  Review
  ::回顾

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  1. What is a first-order reaction?
     ::什么是一阶反应?
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  2. How is the instantaneous rate determined?
     ::瞬时费率是如何确定的?
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  3. How do we determine the rate law and reaction order?
     ::我们如何确定比例法和反应秩序?