Acid-Base Titrations · 酸碱滴定
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| titration curve/taɪˈtreɪʃn kɜːv/ | 滴定曲线 | dī dìng qū xiàn |
| equivalence point/ɪˈkwɪvələns pɔɪnt/ | 等当点 | děng dāng diǎn |
The story a curve tells
- Slowly add base to an acid and track the pH.
- The plot starts low, creeps up, then leaps at one point.
- That steep jump marks the moment of exact neutralization.
- The curve's shape reveals the acid's strength.
曲线讲述的故事
- 慢慢向酸中加入碱,并跟踪 pH。
- 图从低处开始,缓缓上升,然后在某一点跃升。
- 那道陡峭的跃升标记着恰好中和的时刻。
- 曲线的形状揭示酸的强弱。
Reading the titration curve
- The titration curve 滴定曲线 plots pH against added titrant.
- It rises slowly, then jumps sharply at the equivalence point.
- The steep part is where the reaction just completes.
读滴定曲线
- 滴定曲线把 pH 对加入的滴定剂作图。
- 它缓慢上升,然后在等当点急剧跃升。
- 陡峭的部分是反应恰好完成的地方。
A titration curve rises steeply near the equivalence point. · 滴定曲线在等当点附近急剧上升。
The steep jump marks the equivalence point. · 陡峭的跃升标志着等当点。
Where they exactly match
- At the equivalence point 等当点, the moles of acid and base are equal.
- For a strong acid with a strong base, the pH there is 7.
- For a weak acid with a strong base, the pH there is above 7.
恰好相等的地方
- 在等当点,酸和碱的摩尔数相等。
- 对强酸配强碱,那里的 pH 是 7。
- 对弱酸配强碱,那里的 pH 高于 7。
At the equivalence point, the moles of acid and base are... · 在等当点，酸和碱的摩尔数……
Equivalence means the moles exactly match. · 等当意味着摩尔数精确匹配。
For a weak acid titrated with a strong base, the equivalence-point pH is... · 用强碱滴定弱酸时，等当点的pH是……
The leftover conjugate base makes the solution basic. · 剩余的共轭碱使溶液呈碱性。
For a strong acid titrated with a strong base, the equivalence pH is... · 用强碱滴定强酸时，等当点的pH是……
Strong-with-strong gives a neutral salt, so pH is 7. · 强酸与强碱反应生成中性盐，因此pH为7。
The halfway clue
- At the half-equivalence point, half the weak acid is neutralized.
- There, $\text{pH} = \text{p}K_a$ -- a handy shortcut.
- This is also where the buffer is strongest.
中途的线索
- 在半等当点,一半的弱酸被中和。
- 在那里,$\text{pH} = \text{p}K_a$——一个方便的捷径。
- 这也是缓冲能力最强的地方。
The titration curve · 滴定曲线
Track pH as titrant is added; the steep vertical jump marks the equivalence point. · 追踪加入滴定剂时的pH；陡峭的垂直跃升标志着等当点。
At the half-equivalence point of a weak acid titration, pH equals... · 在弱酸滴定的半等当点，pH等于……
Half-neutralized, $\text{pH} = \text{p}K_a$. · 半中和状态，$\text{pH} = \text{p}K_a$。
Titrating a weak acid with a strong base -- is the pH at equivalence exactly 7?
- No: the leftover conjugate base makes it basic.
- The equivalence pH is above 7.
用强碱滴定弱酸——等当点的 pH 恰好是 7 吗?
- 不是:剩下的共轭碱使它呈碱性。
- 等当点 pH 高于 7。
Choose an indicator that changes colour near the ____ point. · 选择变色点接近____处的指示剂。
The endpoint should match the equivalence point. · 终点应与等当点一致。
The equivalence-point pH is not always 7 -- it is 7 only for strong-with-strong; a weak acid gives a basic equivalence point. The half-equivalence point ($\text{pH} = \text{p}K_a$) is different from the equivalence point. And pick an indicator that changes colour near the equivalence pH.
等当点 pH 不总是 7——只有强配强时才是 7;弱酸给出碱性的等当点。半等当点($\text{pH} = \text{p}K_a$)与等当点不同。而且要选一个在等当点 pH 附近变色的指示剂。
A titration curve plots pH against added titrant, jumping steeply at the equivalence point where moles match. That pH is 7 for strong-strong but above 7 for a weak acid with strong base. At the half-equivalence point, $\text{pH} = \text{p}K_a$.
滴定曲线把 pH 对加入的滴定剂作图,在摩尔数相等的等当点急剧跃升。强配强时那个 pH 是 7,而弱酸配强碱时高于 7。在半等当点,$\text{pH} = \text{p}K_a$。