Na_2CO_3对乙酸乙酯皂化反应速率常数测定结果的影响
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摘要
氢氧化钠易吸收空气中的二氧化碳生成碳酸钠.如果配置的氢氧化钠溶液中含有碳酸钠,就会影响其浓度的准确标定,进而影响乙酸乙酯皂化反应速率常数的测定结果.通过探究反应物中碳酸钠对乙酸乙酯皂化反应速率常数的影响,初步探讨了该实验的改进方案.结果表明:随着碳酸钠浓度的不断增加,测得的反应速率常数不断增大;但当碳酸钠的浓度增大到一定浓度后,反应速率常数测定值变化趋于平缓;当碳酸钠的浓度超过0.010mol/L时,测得的反应速率常数数值急剧变小,这可能是由于实际氢氧化钠溶液浓度远低于标定值的原因造成的.建议:利用稀释饱和氢氧化钠溶液的方法配置实验所需的氢氧化钠溶液.该方法既省时,又可以尽量避免碳酸钠对实验结果的影响,适合在本科生物理化学实验教学中进行推广.
Sodium hydroxide,when exposed to the air,will react with the carbon dioxide,to form sodium carbonate.It is very hard to determine the exact concentration of the sodium hydroxide solution,which contains a small amount of sodium carbonate.Sodium carbonate in sodium hydroxide is one of the factors that affect the accuracy of the experimental results on the determination of the rate constant of saponification ethyl acetate.By investigating the influence of sodium carbonate on the rate constant of ethyl acetate saponification in the reactants,the improved scheme of the experiment was discussed.The results show that the measured reaction rate constant increases with the increase of sodium carbonate concentration.However,when the concentration of sodium carbonate increases to a certain concentration,the change of reaction rate constant value tends to be flat;when the concentration of sodium carbonate Above 0.010 mol/L,the measured value of the reaction rate constant sharply decreases,which may be due to the fact that the actual sodium hydroxide solution concentration is far below the calibration value.We suggest that the scheme of preparing the sodium hydroxide solution by dilution with the saturated sodium hydroxide solution can not only save time,but also avoid the effect of sodium carbonate on the experimental results.And this change is suitable for promotion in the teaching of physical chemistry experiments for undergraduates.
Sodium hydroxide,when exposed to the air,will react with the carbon dioxide,to form sodium carbonate.It is very hard to determine the exact concentration of the sodium hydroxide solution,which contains a small amount of sodium carbonate.Sodium carbonate in sodium hydroxide is one of the factors that affect the accuracy of the experimental results on the determination of the rate constant of saponification ethyl acetate.By investigating the influence of sodium carbonate on the rate constant of ethyl acetate saponification in the reactants,the improved scheme of the experiment was discussed.The results show that the measured reaction rate constant increases with the increase of sodium carbonate concentration.However,when the concentration of sodium carbonate increases to a certain concentration,the change of reaction rate constant value tends to be flat;when the concentration of sodium carbonate Above 0.010 mol/L,the measured value of the reaction rate constant sharply decreases,which may be due to the fact that the actual sodium hydroxide solution concentration is far below the calibration value.We suggest that the scheme of preparing the sodium hydroxide solution by dilution with the saturated sodium hydroxide solution can not only save time,but also avoid the effect of sodium carbonate on the experimental results.And this change is suitable for promotion in the teaching of physical chemistry experiments for undergraduates.
引文
[1]复旦大学编.物理化学实验[M].3版.北京:高等教育出版社,2004:103-107.
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[5]李林尉,杜凌云,王芳,等.化学动力学介质效应研究(Ⅰ)---混合溶剂中乙酸乙酯碱性催化水解反应速率常数的测定(298.15K)[J].聊城大学学报(自然科学版),2004,17(3):36-38.
[6]张来英,陈良坦,李海燕.乙酸乙酯皂化反应的热动力学实验[J].大学化学,2015,30(2):56-59.
[7]李水清,张钟宁,谢晖.微波辐射对乙酸乙酯皂化反应的影响[J].化学研究,2005,16(3):47-49.
[8]陈书鸿,张丽莹,乐艳,等.乙酸乙酯皂化反应速率常数测定实验的改进[J].重庆三峡学院学报,2016,32(3):61-64.
[9]李森兰.乙酸乙酯皂化反应速度常数测定实验研究[J].洛阳师范学院学报,2004(2):54-57.
[10]谢祖芳,黎中良,黄中强,等.乙酸乙酯皂化反应实验数据的非线性处理[J].实验科学与技术,2006,4(6):1-3.
[11]凌锦龙.乙酸乙酯皂化反应实验数据处理方法的改进[J].通化师范学院学报,2005,26(2):49-51.
[12]玉占君,张文伟,任庆云.电导法测定乙酸乙酯皂化反应速率常数的一种数据处理方法[J].辽宁师范大学学报(自然科学版),2006,29(4):511-512.
[13]玉占君,冯春梁.物理化学实验[M].北京:化学工业出版社,2014:61-66.
[14]白云山,陈琳,史佳妮,等.电导法测定乙酸乙酯皂化反应速率常数的实验改进[J].高校实验室工作研究,2015(4):140-142.
[2]杨桂株,初晓峰,吕楠.乙酸乙酯皂化反应速率常数测定法改进的实验性研究[J].吉林师范学院学报,1997,18(1):71-74.
[3]骆定法,冯铁臣.乙酸乙酯皂化反应动力学实验中的异常现象探讨[J].信阳师范学院学报(自然科学版),1997,10(2):38-40.
[4]周卓媛,汪存信,屈松生,等.用高效液相色谱法研究乙酸乙酯皂化反应动力学[J].武汉大学学报(自然科学版),1989(3):59-62.
[5]李林尉,杜凌云,王芳,等.化学动力学介质效应研究(Ⅰ)---混合溶剂中乙酸乙酯碱性催化水解反应速率常数的测定(298.15K)[J].聊城大学学报(自然科学版),2004,17(3):36-38.
[6]张来英,陈良坦,李海燕.乙酸乙酯皂化反应的热动力学实验[J].大学化学,2015,30(2):56-59.
[7]李水清,张钟宁,谢晖.微波辐射对乙酸乙酯皂化反应的影响[J].化学研究,2005,16(3):47-49.
[8]陈书鸿,张丽莹,乐艳,等.乙酸乙酯皂化反应速率常数测定实验的改进[J].重庆三峡学院学报,2016,32(3):61-64.
[9]李森兰.乙酸乙酯皂化反应速度常数测定实验研究[J].洛阳师范学院学报,2004(2):54-57.
[10]谢祖芳,黎中良,黄中强,等.乙酸乙酯皂化反应实验数据的非线性处理[J].实验科学与技术,2006,4(6):1-3.
[11]凌锦龙.乙酸乙酯皂化反应实验数据处理方法的改进[J].通化师范学院学报,2005,26(2):49-51.
[12]玉占君,张文伟,任庆云.电导法测定乙酸乙酯皂化反应速率常数的一种数据处理方法[J].辽宁师范大学学报(自然科学版),2006,29(4):511-512.
[13]玉占君,冯春梁.物理化学实验[M].北京:化学工业出版社,2014:61-66.
[14]白云山,陈琳,史佳妮,等.电导法测定乙酸乙酯皂化反应速率常数的实验改进[J].高校实验室工作研究,2015(4):140-142.