一元弱酸准确滴定的实验设计:滴定误差与单滴变色

Experimental Design for Accurate Titration of a Weak Monoprotic Acid Solution:Titration Error and Solution Color Change

滴定一元弱酸HA溶液时,通常需要满足以下要求:(1)滴定突跃范围≥0.60pH,(2)计量点附近,加入半滴或1滴NaOH溶液会导致HA溶液颜色突变。设计滴定实验时,除了考虑滴定误差,还必须同时考虑单滴变色问题。假设滴定允许误差为±0.5%,如果用0.5000 mol×L^(-1) NaOH滴定20.00 mL 0.1000 mol×L^(-1) HA溶液,则化学计量点消耗NaOH溶液4.00 mL,滴定管半滴液滴体积0.02 mL,滴定误差恰为±0.5%。

When titrating a weak monoprotic acid(HA)solution,it is usually necessary to meet the following requirements:(1)Titrating jump range≥0.60pH,(2)Near the stoichiometric point,adding half drop or one drop NaOH solution will change the color of HA solution dramatically.In the titration experiment,not only the titration error but also the color change of HA solution should be considered.If the allowable error of titration is±0.5%,the experiment can be carried out by titrating 20.00 mL 0.1000 mol×L^(-1) HA solution with 0.5000 mol×L^(-1) NaOH solution.The stoichiometric point consumes 4.00 mL of NaOH solution and the half drop volume of the burette is 0.02 mL,the titration error is exactly±0.5%.