关于化学反应速度常数的探讨

THE RESEARCH ON THE SPECIFIC RATECONSTANT OF CHEMICAL REACTION

反应速度的单位是摩·升－１·时间－１，大多数为ｍｏｌ·ｌ－１·ｓ－１或ｍｏｌ·ｌ－１·ｍｉｎ－１。速度常数ｋ的单位取决于反应的级数，例如一级反应，速度常数的单位为ｓ－１，二级反应速度常数的单位是ｌ·ｍｏｌ－１·ｓ－１。对于可逆反应，当反应达平衡时，正逆反应的速度相等，得到Ｋ＝ｋｆ／ｋｒ。如果正逆反应的反应级数不同，所得的平衡常数Ｋ就有量纲。由热力学数据计算所得的平衡常数是无量纲的。为使热力学平衡Ｋ与Ｋ＝ｋｆ／ｋｒ所得的Ｋ一致，速度常数的单位只能是ｍｏｌ·ｌ－１·ｓ－１或ｍｏｌ·ｌ－１·ｍｉｎ－１。

The units of the rate of any reaction are moles per liter per unit time, and may be mol·l-1·s-1 or mol·l-1·min-1. The units of the specific rate constant, k, depend on the order of the reaction. For example, for a first-order reaction, the unit of the specific rate constant is s-1. For a second-order reaction, the unit of k is l·mol-1·s-1. For a reversible reaction, when the system reachs equilibrium, however, the rates of the forward and reverse reaction must be equal. We obtain, at equilibrium, K=kf/kr. When order reaction of the forward reaction is not equal to that reverse reaaction, we find, equilibrium constant has dimension. The thermodynamics equilibrium constant is dimensionless. For the thermodynamics equilibrium constant is equal to that K=kf/kr, the units of the specific rate constant, k, can be only mol·l-1·s-1 or mol·l-1·min-1.