Weak Acid and Base Equilibria · 弱酸和弱碱平衡
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| acid dissociation constant/ˈæsɪd dɪˌsəʊsɪˈeɪʃn ˈkɒnstənt/ | 酸解离常数 | suān jiě lí cháng shù |
The ones that only partly let go
- A strong acid dumps all its protons at once.
- But most acids hold on and release only a fraction.
- That partial release settles into an equilibrium.
- A constant measures just how far it goes.
只肯放开一部分的那些
- 强酸一次性把它所有的质子都倒出去。
- 但大多数酸抓着不放,只释放一小部分。
- 那份部分释放稳定成一个平衡。
- 一个常数衡量它走了多远。
The acid dissociation constant
- A weak acid ionizes partly: $\text{HA} \rightleftharpoons \text{H}^+ + \text{A}^-$.
- The acid dissociation constant 酸解离常数 is $K_a = \dfrac{[\text{H}^+][\text{A}^-]}{[\text{HA}]}$.
- A larger $K_a$ means a stronger weak acid.
酸解离常数
- 弱酸部分电离:$\text{HA} \rightleftharpoons \text{H}^+ + \text{A}^-$。
- 酸解离常数是 $K_a = \dfrac{[\text{H}^+][\text{A}^-]}{[\text{HA}]}$。
- 更大的 $K_a$ 意味着更强的弱酸。
A larger $K_a$ means the weak acid is... · 更大的$K_a$意味着该弱酸……
A bigger $K_a$ means more ionization -- a stronger weak acid. · 更大的$K_a$意味着更多电离——更强的弱酸。
The base version
- A weak base has a $K_b$ describing its partial reaction with water.
- A larger $K_b$ means a stronger weak base.
- Both work like any equilibrium constant.
碱的版本
- 弱碱有一个 $K_b$,描述它与水的部分反应。
- 更大的 $K_b$ 意味着更强的弱碱。
- 两者都像任何平衡常数一样运作。
The constant describing a weak base's reaction with water is... · 描述弱碱与水反应的常数是……
$K_b$ is the base dissociation constant. · $K_b$是碱解离常数。
Finding the pH
- Set up an ICE table with the small ionization $x$.
- Solve $K_a$ for $x = [\text{H}^+]$, then take $-\log$.
- Percent ionization is $x$ divided by the starting acid.
求 pH
- 建一张三段式表,用小的电离量 $x$。
- 解 $K_a$ 求 $x = [\text{H}^+]$,再取 $-\log$。
- 电离百分数是 $x$ 除以起始酸。
Strong or weak? · 强还是弱？
Sort each acid or base by whether it ionises fully or only partly. · 根据每种酸或碱是完全电离还是部分电离，对其进行排序。
For a weak acid, $[\text{H}^+]$ equals the acid's full concentration. · 对于弱酸，$[\text{H}^+]$等于酸的总浓度。
Only strong acids ionize fully; a weak acid needs $K_a$. · 只有强酸完全电离；弱酸需要$K_a$。
Percent ionization is the amount ionized divided by the ____ amount of acid. · 百分比电离是被电离的量除以酸的____量。
It compares $x$ to the initial acid concentration. · 它将$x$与初始酸浓度进行比较。
A weak acid barely ionizes. How does its pH compare with a strong acid of the same concentration?
- The weak acid releases fewer $\text{H}^+$ ions.
- So its pH is higher (less acidic) than the strong acid.
一种弱酸几乎不电离。它的 pH 与相同浓度的强酸相比如何?
- 弱酸释放更少的 $\text{H}^+$ 离子。
- 所以它的 pH 比强酸高(酸性更弱)。
A weak acid and a dilute acid are the same thing. · 弱酸和稀酸是同一种东西。
Weak is about ionization; dilute is about concentration. · “弱”指电离程度；“稀”指浓度。
Compared with a strong acid of the same concentration, a weak acid has a... · 与同浓度的强酸相比，弱酸的……
Less ionization means fewer $\text{H}^+$ and a higher pH. · 较少电离意味着较少的$\text{H}^+$和较高的pH。
A weak acid is not the same as a dilute one -- "weak" means partly ionized, "dilute" means low concentration. Do not assume $[\text{H}^+]$ equals the acid's concentration for a weak acid; use $K_a$. And a bigger $K_a$ is a stronger acid, but it is still weak.
弱酸与稀酸不是一回事——"弱"意味着部分电离,"稀"意味着浓度低。对弱酸,不要假设 $[\text{H}^+]$ 等于酸的浓度;要用 $K_a$。而且更大的 $K_a$ 是更强的酸,但它仍然是弱酸。
A weak acid only partly ionizes, described by the acid dissociation constant $K_a = [\text{H}^+][\text{A}^-]/[\text{HA}]$ (a weak base has a $K_b$). A larger $K_a$ is a stronger weak acid. Find the pH with an ICE table and $K_a$ -- do not assume $[\text{H}^+]$ equals the concentration.
弱酸只部分电离,由酸解离常数 $K_a = [\text{H}^+][\text{A}^-]/[\text{HA}]$ 描述(弱碱有一个 $K_b$)。更大的 $K_a$ 是更强的弱酸。用三段式表和 $K_a$ 求 pH——不要假设 $[\text{H}^+]$ 等于浓度。