含义Meaning
用任一物质浓度随时间的变化率除以其计量数（反应物为负）得到的速率，与选哪种物质无关。
The rate of change of any species’ concentration divided by its stoichiometric number (negative for reactants) — the same whichever species is used.
符号说明Symbols
| 符号Symbol | 含义 Meaning | 单位 Unit |
|---|---|---|
| \(v\) | 反应速率rate of reaction | mol·L⁻¹·s⁻¹ |
| \(\nu_\mathrm B\) | 计量数（反应物取负）stoichiometric number (negative for reactants) | 1 |
推导Derivation
对 aA + bB → cC + dD，各物质变化率之比等于计量数之比。
For aA + bB → cC + dD the rates of change are in the ratio of coefficients.
除以各自计量数后得到唯一的反应速率：\(v = -\frac1a\frac{d[\mathrm A]}{dt} = \frac1c\frac{d[\mathrm C]}{dt}\)。
Dividing by coefficients gives a single rate.
中学常用某段时间内的平均速率；瞬时速率是浓度–时间曲线的切线斜率。
Average rates over an interval; the instantaneous rate is the tangent slope.
适用条件与局限Assumptions & limitations
定义要求恒容（体积变化时用反应进度 \(\dot\xi/V\)）；有中间物积累时各物质速率不再同步。
Assumes constant volume; intermediates break the simple ratios.
例题Worked example
N₂ + 3H₂ → 2NH₃：若 d[NH₃]/dt = 0.2 mol/(L·s)，则 v = 0.1，d[H₂]/dt = −0.3 mol/(L·s)。
N₂ + 3H₂ → 2NH₃: d[NH₃]/dt = 0.2 gives v = 0.1 and d[H₂]/dt = −0.3.