The Reaction Quotient and Equilibrium Constant · 反应商与平衡常数
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| equilibrium constant/ˌiːkwɪˈlɪbrɪəm ˈkɒnstənt/ | 平衡常数 | píng héng cháng shù |
| reaction quotient/rɪˈækʃn ˈkwəʊʃənt/ | 反应商 | fǎn yìng shāng |
A number that predicts direction
- At balance, a special ratio of products to reactants stays fixed.
- Compute that same ratio at any moment and compare.
- The comparison tells you which way the reaction will go.
- Two symbols, one powerful tool.
一个预测方向的数
- 在平衡时,产物与反应物的一个特殊比值保持固定。
- 在任意时刻计算同样的比值并比较。
- 这个比较告诉你反应会往哪个方向进行。
- 两个符号,一个强大的工具。
The equilibrium constant K
- The equilibrium constant 平衡常数 $K$ is the fixed ratio at equilibrium:
- Each concentration is raised to its coefficient.
平衡常数 K
- 平衡常数 $K$ 是平衡时那个固定的比值:
- 每个浓度都升到它的系数次方。
In the expression for $K$, each concentration is raised to its... · 在 $K$ 的表达式中，每个浓度都提升至其...
Concentrations are raised to their balanced coefficients. · 浓度提升至其配平系数。
The reaction quotient Q
- The reaction quotient 反应商 $Q$ has the same form, but at any moment.
- It measures where the reaction currently stands.
- At equilibrium, $Q = K$.
反应商 Q
- 反应商 $Q$ 有相同的形式,但在任意时刻。
- 它衡量反应当前处于什么位置。
- 在平衡时,$Q = K$。
At equilibrium, $Q$ equals $K$. · 在平衡时，$Q$ 等于 $K$。
When $Q = K$, the system is at equilibrium. · 当 $Q = K$ 时，系统处于平衡状态。
The reaction quotient $Q$ is like $K$ but measured at the current ____. · 反应商 $Q$ 类似于 $K$，但在当前的____测量。
$Q$ uses the same expression at any instant, not only at equilibrium. · $Q$ 在任何瞬间使用相同的表达式，而不仅仅是在平衡时。
Predicting the direction
- If $Q < K$, there are too few products, so it shifts forward.
- If $Q > K$, there are too many products, so it shifts backward.
- If $Q = K$, it is already at equilibrium.
预测方向
- 若 $Q < K$,产物太少,所以它正向移动。
- 若 $Q > K$,产物太多,所以它逆向移动。
- 若 $Q = K$,它已处于平衡。
What goes into K? · K 中包含什么？
Sort each species by whether it appears in the equilibrium expression. · 按是否出现在平衡表达式中对每种物种进行分类。
If $Q < K$, the reaction shifts... · 如果 $Q < K$，反应将向...
Too few products means it moves forward to make more. · 产物太少意味着反应向前移动以生成更多产物。
If $Q > K$, the reaction shifts... · 如果 $Q > K$，反应将向...
Too many products means it moves backward. · 产物太多意味着反应向后移动。
A reaction has $K = 10$ but currently $Q = 2$. Which way does it go?
- $Q < K$, so there are too few products.
- The reaction shifts forward to make more.
某反应 $K = 10$,但当前 $Q = 2$。它往哪个方向进行?
- $Q < K$,所以产物太少。
- 反应正向移动以生成更多。
Pure solids and liquids are left out of the $K$ expression. · 纯固体和液体被排除在 $K$ 表达式之外。
Only gases and aqueous species appear in $K$. · 只有气体和水溶液物种出现在 $K$ 中。
$Q$ and $K$ use the same expression -- $Q$ is just "$K$ right now," before equilibrium. Include only gases and aqueous species; pure solids and liquids are left out. And compare: $Q < K$ goes forward, $Q > K$ goes backward.
$Q$ 和 $K$ 用的是相同的表达式——$Q$ 只是"此刻的 $K$",在平衡之前。只包含气体和水溶液物种;纯固体和液体不列入。而且比较:$Q < K$ 正向,$Q > K$ 逆向。
The equilibrium constant $K$ is the products-over-reactants ratio (each to its coefficient) at equilibrium. The reaction quotient $Q$ is the same ratio at any moment. Comparing them predicts direction: $Q < K$ shifts forward, $Q > K$ backward, $Q = K$ is equilibrium.
平衡常数 $K$ 是平衡时产物比反应物的比值(各升到系数次方)。反应商 $Q$ 是任意时刻的相同比值。比较它们能预测方向:$Q < K$ 正向移动,$Q > K$ 逆向,$Q = K$ 是平衡。