2. 外语
  3. About a century ago, the Swedish physical scientist Arrhenius proposed a low of classical chemistry that relates chemical reacti

About a century ago, the Swedish physical scientist Arrhenius proposed a low of classical chemistry that relates chemical reacti

admin2014-12-26  28
问题     About a century ago, the Swedish physical scientist Arrhenius proposed a low of classical chemistry that relates chemical reaction rate to temperature. According to his equation, chemical reactions are increasingly unlikely to occur as temperature approaches absolute zero, and at absolute zero, reactions stop. However, recent experiment evidence reveals that although the Arrhenius equation is generally accurate in describing the kind of chemical reaction that occurs at relatively high temperature, at temperatures closer to zero a quantum-mechanical effect known as tunneling comes into play; this effect accounts for chemical reactions that are forbidden by me principles of classical chemistry. Specifically, entire molecules can tunnel through the barriers of repulsive forces from other molecules and chemically react even though these molecules do not have sufficient energy, according to classical chemistry, to overcome the repulsive barrier.
    The rate of any chemical reaction, regardless of the temperature at which it takes place, usually depends on a very important characteristic known as its activation energy. Any molecule can be imagined to reside at the bottom of a so-called potential well of energy. A chemical reaction corresponds to the transition of a molecule from the bottom of one potential well to the bottom of another. In classical chemistry, such a transition can be accomplished only by going over the potential barrier between the well, the height of which remains constant and is called the activation energy of the reaction. In tunneling, the reactings molecules tunnel from the bottom of one to the bottom of another well without having to rise over the barrier between the two wells. Recently researchers have developed the concept of tunneling temperature: the temperature below which tunneling transitions greatly outnumber Arrhenius transitions, and classical mechanics gives way to its quantum counterpart.
    This tunneling phenomenon at very low temperatures suggested my hypothesis about a cold prehistory of life: formation of rather complex organic molecules in the deep cold of outer space, where temperatures usually reach only a few degrees Kelvin. Cosmic rays might trigger the synthesis of simple molecules, such as interstellar formaldehyde, in dark clouds of interstellar dust. Afterward complex organic molecules would be formed, slowly but surely, by means of tunneling. After I offered my hypothesis, Hoyle and Wickramashinghe argued that molecules of interstellar formaldehyde have indeed evolved into stable polysaccharides such as cellulose and starch. Their conclusions, although strongly disputed, have generated excitement among investigators such as myself who are proposing that the galactic clouds are the places where the prebiological evolution of compounds necessary to life occurred.
According to the Arrhenius equations as discussed in the passage, which of the following statements about chemical reactions is true?
选项 A、Chemical reactions are less likely to occur at temperature close to absolute zero.
B、In some cases the rate of a chemical reaction is related to temperature and in other cases it is not.
C、The rate of a chemical reaction depends on many other factors besides temperature.
D、Chemical reaction rate and temperature are not related.
答案A
解析 细节题。根据“Arrhenius equations”定位至文章第一段According to hisequation，chemical reactions are increasingly unlikely to occur as temperatureapproaches absolute zero，and at absolute zero，reactions stop．“根据他的定理，当温度越接近绝对零度，化学反应就越不可能发生；当到达绝对零度的时候，反应就停止了。”这和A选项表达一致。所以答案选A。
转载请注明原文地址:https://kaotiyun.com/show/6bh7777K
0

大学英语六级

相关试题推荐
随机试题
最新回复(0)