章节大纲

  • A large ammonia storage tank with a warning against methamphetamine production.

    What is the dual purpose here?
    ::这里的双重目的是什么?

    The ammonia storage tank in the picture above does two things, One it stores ammonia at high pressure to minimize the reverse reaction that would lead to less ammonia and more nitrogen and hydrogen. Secondly, it sends an important message. Ammonia is used to make methamphetamine, a dangerous drug of abuse. Locks and other safety mechanisms built into the tanks help stop the theft of ammonia to be used in this illicit activity.
    ::上面提到的氨储罐有两件事:一是高度压力储存氨,以尽量减少导致氨减少、氮和氢含量增加的反反应;二是发出一个重要信息:氨用于制造甲基安非他明,这是一种危险的滥用药物;三是罐装的锁和其他安全机制,有助于阻止氨被偷用于这种非法活动。

    Effect of Pressure
    ::压力效应

    Changing the pressure of an equilibrium system in which are involved is also a stress to the system. A change in the pressure on a or a solid has a negligible effect. We will return again to the equilibrium for the Haber-Bosch process. Imagine the gases are contained in a closed system in which the volume of the system is controlled by an adjustable piston as shown in  Figure .
    ::改变所涉及的平衡系统的压力也是对系统的压力。 改变对一个或一个固体的压力影响微不足道。 我们将再次回到Haber-Bosch过程的平衡。 想象一下气体存在于封闭系统中,在这个系统中,系统的体积由可调整的活塞控制,如图所示。

    Three containers showing effects of pressure on gas reactions: initial state, increased pressure, and forward reaction favoring ammonia.

    Effect of pressure on ammonia formation.
    ::压力对氨形成的影响。

    On the far left, the reaction system contains primarily N 2 and H 2 , with only one molecule of NH 3 present. As the piston is pushed inwards, the pressure of the system increases according to Boyle’s Law . This is a stress to the equilibrium. In the middle image, the same number of molecules is now confined in a smaller space and so the pressure has increased. According to LeChâtelier’s principle, the system responds in order to relieve the stress. In the image on the right, the forward reaction has been favored, in which one molecule of N 2 combines with three molecules of H 2 to form two molecules of NH 3 . The overall result is a decrease in the number of gas molecules in the entire system. This in turn decreases the pressure and provides a relief to the original stress of a pressure increase. An increase in pressure on an equilibrium system favors the reaction which produces fewer total moles of gas. In this case, it is the forward reaction that is favored.
    ::在最左端,反应系统主要包含N2和H2, 只有一个NH3分子。 随着活塞被推入, 系统的压力会根据Boyle法增加。 这是对平衡的压力。 在中间图像中, 同样的分子数量现在被局限在较小空间, 压力因此增加。 根据Lechâtiierer的原则, 系统的反应有利于缓解压力。 在右边的图像中, 前进反应是有利的, 其中一分子N2与三个H2分子结合, 形成NH3的两种分子。 总体结果是整个系统中的气体分子数量减少。 这反过来会降低压力, 减轻原先的压力。 平衡系统的压力增加有利于产生较少气体总分子的反应。 在这种情况下, 正面反应是有利的。

    A decrease in pressure on the above system could be achieved by pulling the piston outward, increasing the container volume. The equilibrium would respond by favoring the reverse reaction in which NH 3 decomposes to N 2 and H 2 . This is because the overall number of gas molecules would increases and so would the pressure. A decrease in pressure on an equilibrium system favors the reaction which produces more total moles of gas. This is summarized in  Table .
    ::通过拉动活塞向外拉动,增加容器体积,可以减少上述系统的压力。这种平衡将有利于NH3分解到N2和H2的反向反应。这是因为气体分子的总数会增加,压力也会增加。平衡系统的压力减少有利于产生更多气内毫微粒的反应。这一点在表格中概述。

    Stress Response
    pressure increase reaction produces fewer gas molecules
    pressure decrease reaction produces more gas molecules

    Like changes in , the  K e q value for a given reaction is unchanged by a change in pressure.
    ::与特定反应的Keq值变化一样,特定反应的Keq值因压力变化而保持不变。

    It is important to remember when analyzing the effect of a pressure change on equilibrium that only gases are affected. If a certain reaction involves liquids or solids, they should be ignored. Calcium carbonate decomposes according to the equilibrium reaction:
    ::在分析压力变化对仅影响气体的平衡的影响时,必须记住这一点。 如果某种反应涉及液体或固体,就应该忽略这些反应。 碳酸钙根据平衡反应分解:

    CaCO 3 ( s ) ⇄ CaO ( s ) + O 2 ( g )


    ::CaCO3 +CaO +O2(g)

    Oxygen is the only gas in the system. An increase in the pressure of the system slows the rate of decomposition of CaCO 3 because the reverse reaction is favored. When a system contains equal moles of gas on both sides of the equation, pressure has no effect on the equilibrium position, as in the formation of HCl from H 2 and Cl 2 .
    ::氧气是系统中唯一的气体。 系统压力的增加会减缓CaCO3的分解速度, 因为反向反应有利。 当一个系统在方程的两侧都含有相等的气体摩尔时, 压力对平衡位置没有影响, 比如H2 和 Cl2 形成HCl时, 压力对平衡位置没有影响。

    H 2 ( g ) + Cl 2 ( g ) ⇄ 2 HCl ( g )


    ::H2(g) +Cl2(g) 2HCl(g)

     

     

    Summary
    ::摘要

    • The influence of pressure on an equilibrium system is described.
      ::报告叙述了压力对平衡系统的影响。

    Review
    ::回顾

    1. Why does the pressure increase in the middle picture?
      ::为什么中观的压力会增加?
    2. How is the stress due to increased pressure relieved?
      ::如何减轻因压力增加而产生的压力?
    3. Why does an increase in pressure slow the rate of CaCO 3 decomposition?
      ::为什么压力的增加会减缓CaCO3分解的速度?