酸碱滴定Acid–base titration

用移液管准确量取 25.00 cm³ 待测溶液放入锥形瓶，加 2–3 滴指示剂。滴定管先用标准溶液润洗，装液后读取初始读数。边滴加边摇动锥形瓶，接近终点时逐滴加入，直到指示剂颜色突变且半分钟内不褪去。重复滴定，直到相邻两次结果相差不超过 0.10 cm³，取平均值计算。

Pipette exactly 25.00 cm³ of the solution into a conical flask and add 2–3 drops of indicator. Rinse the burette with the standard solution, fill it and record the initial reading. Add the titrant while swirling, then dropwise near the end point, until the indicator changes colour and the change lasts for half a minute. Repeat until two consecutive titres agree within 0.10 cm³, and use their mean.

等当点是酸和碱按化学计量关系恰好完全反应的点，终点是指示剂变色的点，选择合适的指示剂使二者尽量接近。在等当点附近，加入极少量滴定剂就会使 pH 发生突跃。强酸滴定强碱的突跃约为 pH 3–11，甲基橙和酚酞都可用；弱酸滴定剂与强碱的突跃在碱性区，用酚酞；强酸与弱碱的突跃在酸性区，用甲基橙；弱酸与弱碱没有明显突跃，不宜用指示剂。

The equivalence point is where acid and base have reacted in exact stoichiometric amounts; the end point is where the indicator changes, and the indicator is chosen to make them as close as possible. Near equivalence a tiny addition causes a sharp jump in pH. For strong acid–strong base the jump spans about pH 3–11, so methyl orange or phenolphthalein works; for weak acid–strong base it lies in the alkaline range, so phenolphthalein is used; for strong acid–weak base it lies in the acid range, so methyl orange is used; weak acid–weak base gives no sharp jump and suits no indicator.

先由标准溶液的浓度和体积求出其物质的量，再按化学方程式的计量比求待测物的物质的量，最后除以待测溶液体积。例：22.50 cm³ 0.100 mol dm⁻³ HCl 恰好中和 25.00 cm³ NaOH，n(NaOH) = n(HCl) = 2.250 × 10⁻³ mol，c(NaOH) = 0.0900 mol dm⁻³。

Find the amount of the standard from its concentration and volume, use the mole ratio in the equation to get the amount of the analyte, and divide by the analyte's volume. Example: 22.50 cm³ of 0.100 mol dm⁻³ HCl neutralises 25.00 cm³ of NaOH, so n(NaOH) = n(HCl) = 2.250 × 10⁻³ mol and c(NaOH) = 0.0900 mol dm⁻³.