Course: 19.3 平衡常量(Keq)

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平衡常量 (Keq)
What is carbon monoxide poisoning?
::什么是一氧化碳中毒?

Red blood cells transport oxygen to the tissues so they can function. In the absence of oxygen, cells cannot carry out their biochemical responsibilities. Oxygen moves to the cells attached to hemoglobin, a found in the red cells. In cases of carbon monoxide poisoning, CO binds much more strongly to the hemoglobin, blocking oxygen attachment and lowering the amount of oxygen reaching the cells. Treatment involves the patient breathing pure oxygen to displace the carbon monoxide. The equilibrium reaction shown below illustrates the shift toward the right when excess oxygen is added to the system :
::红血细胞将氧输送到组织中,这样它们就能正常工作。在没有氧气的情况下,细胞无法履行其生化责任。氧气转移到红细胞中发现的血红蛋白的附着细胞。在一氧化碳中毒的情况下,二氧化碳与血红蛋白结合的强度要大得多,阻断氧附件,降低进入细胞的氧量。治疗涉及病人呼吸纯氧以取代一氧化碳。下面显示的平衡反应表明当系统增加过量氧气时向右的转变:

$\begin{aligned} Hb (CO)_{4} (a q) + 4 O_{2} (g) ⇋ Hb (O_{2})_{4} (a q) + 4 CO (g) \end{aligned}$
$\begin{align*}\text{Hb}(\text{CO})_4(aq) + 4\text{O}_2 (g) \leftrightharpoons \text{Hb}(\text{O}_2)_4(aq) + 4\text{CO} (g)\end{align*}$
::H(CO)4(aq)+4O2(g)Hb(O2)4(aq)+4CO(g)

Equilibrium Constant
::平衡常数

Consider the hypothetical in which reactants $\begin{align*}A\end{align*}$ and $\begin{align*}B\end{align*}$ react to form products $\begin{align*}C\end{align*}$ and $\begin{align*}D\end{align*}$ . This equilibrium can be shown below, where the lower case letters represent the coefficients of each substance .
::考虑反应剂A和B对形成产品C和D作出反应的假设。这一平衡如下表所示,较低的案例字母代表每种物质的系数。

$\begin{aligned} a A + b B ⇄ c C + d D \end{aligned}$
$\begin{align*}aA + bB \rightleftarrows cC+dD\end{align*}$
::aA+bB+cC+dD+A+B+B+C+D+B+C+D+B+C+C+D+D+B+C+C+D+C+D+D+B+C+C+C+D+C+D+D+D+A+B+C+CC+C+D+D+D+D+D+C+C+D+C+D+D+C+D+C+D+D+C+C+C+D+D+D+D+D+D+D+D+C+C+C+C+C+C+D+D+D+D+D+D+D+dD+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+A+A+A+B+C+C+cC+C+C+C+C+dD+dD+dD+dD+D+dD+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+D+

As we have established, the rates of the forward and reverse reactions are the same at equilibrium, and so the of all of the substances are constant. Since that is the case, it stands to reason that a ratio of the concentrations for any given reaction at equilibrium maintains a constant value. The equilibrium constant $\begin{align*}(K_{eq})\end{align*}$ is the ratio of the mathematical product of the concentrations of the products of a reaction to the mathematical product of the concentrations of the reactants of the reaction. Each concentration is raised to the power of its coefficient in the balanced chemical equation . For the general reaction above, the equilibrium constant expression is written as follows:
::正如我们已经确定的那样,前方和反向反应的速率在平衡时是相同的,因此所有物质的速率都是不变的。由于情况如此,因此有理由认为,平衡时任何特定反应的浓度比率保持一个不变值。平衡常数(Keq)是反应反应反应者浓度的数学产品对数学产品反应的数学产品浓度的比。每种浓度都提高到平衡化学方程式中系数的功率。对于上文的一般反应,平衡常数表达方式如下:

$\begin{aligned} K_{e q} = \frac{{[C]}^{c} {[D]}^{d}}{{[A]}^{a} {[B]}^{b}} \end{aligned}$
$\begin{align*}K_{eq}=\frac{\left [ C\right ]^c \left [ D\right ]^d}{\left [ A\right ]^a \left [B \right ]^b}\end{align*}$
::Keq=[C]c [D]d[A]a[B]b

The concentrations of each substance, indicated by the square brackets around the formula, are measured in units (mol/L).
::公式前后方括号所示每种物质的浓度以单位(摩尔/升)计量。

The value of the equilibrium constant for any reaction is only determined by . As detailed in the above section, the position of equilibrium for a given reaction does not depend on the starting concentrations and so the value of the equilibrium constant is truly constant. It does, however, depend on the temperature of the reaction. This is because equilibrium is defined as a condition resulting from the rates of forward and reverse reactions being equal. If the temperature changes, the corresponding change in those reaction rates will alter the equilibrium constant. For any reaction in which a $\begin{align*}K_{eq}\end{align*}$ is given, the temperature should be specified.
::任何反应的平衡常量值仅由以下因素决定。如上一节所详述,特定反应的平衡位置并不取决于起始浓度,因此平衡常量的值是真正的恒定的。但是,它取决于反应的温度。这是因为平衡被定义为由前向和反向反应的速率决定的一个条件。如果温度变化,这些反应率的相应变化将改变平衡常数。对于给出 Keq 的任何反应,应指定温度。

Summary
::摘要

The equilibrium constant for a reversible reaction is described.
::描述可逆反应的平衡常数。

Review
::回顾

What does the equilibrium constant tell us?
::平衡常数告诉我们什么?

What does it mean if the $\begin{align*}K_{eq}\end{align*}$ is > 1?
::如果Keq > 1是什么意思?

What does it mean if the $\begin{align*}K_{eq}\end{align*}$ is < 1?
::如果Keq还小于1是什么意思?

Does the position of equilibrium depend on the starting concentrations?
::平衡的位置是否取决于起始浓度?

Section outline

General

平衡常量 (Keq)

What is carbon monoxide poisoning? ::什么是一氧化碳中毒?

Equilibrium Constant ::平衡常数

Summary ::摘要

Review ::回顾

What is carbon monoxide poisoning?
::什么是一氧化碳中毒?

Equilibrium Constant
::平衡常数

Summary
::摘要

Review
::回顾