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Determination of Acetidin Saponification Rate Constant by Conductivity Method

电导法测定乙酸乙酯皂化反应的速率常数. Determination of Acetidin Saponification Rate Constant by Conductivity Method. 退出. contents. Purposes and Demands Principle Apparatus and Reagent Procedure Data Records and Processing Questions Attentions Demonstrated. Purposes and Demands.

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Determination of Acetidin Saponification Rate Constant by Conductivity Method

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  1. 电导法测定乙酸乙酯皂化反应的速率常数 Determination of Acetidin Saponification Rate Constant by Conductivity Method 退出

  2. contents • Purposes and Demands • Principle • Apparatus and Reagent • Procedure • Data Records and Processing • Questions • Attentions • Demonstrated

  3. Purposes and Demands • 1.Acquire the conductivity method to determine acetidin saponification rate constant and know how to determine activation energy. • 2.Learn properties of the second degrees reaction and the illustration method which used to determine the reaction constant by.

  4. Principle Acetidin Saponification is a second degrees reaction： t=0 C C 0 0 t=t C－x C－x x x t→∞ →0 →0 →C →C

  5. Rate equation can be written as： of which can be integrated to ： Where k is rate constant.

  6. Ionic equation is： Na+、 CH3COO－ 、 OH－ ions is electric in the solution and through the reaction progress, concentration of some ions change. Concentration of OH－ decrease when CH3COO－increase and Na+ has no change.

  7. Because molar conductance of OH－is much bigger than CH3COO－ , the conductance of the system can be considered to decline.

  8. When reaction is ongoing, x is expressed to X=B(G0－Gt) ② Where X is addition for NaAc, B is proportion constant, G0 stands for conductivity at the beginning and Gt stands for conductivity in the reaction.

  9. When reaction terminate, concentration c is expressed to C=B(G0－G∞) ③ Where G∞ stands for the conductivity at the same time reaction terminate.

  10. Adding equations .② and .③ to equation .①, we obtain： （4） Where C is initiative concentration of solution. Graph of gainst t should give a straight line of slope (m=CK ). K is rate constant and its unit is min－1·mol－1·dm3.

  11. Apparatus and Reagent • DDS-ⅡA Conductivity detector 1 • Thermostatic trough 1 • Bouble-tube conductance cell 2 • Pipette (10ml) 2 • Iodine flask 1 • Stopping watch 1 • NaOH (0.0100mol•dm3confectfresh） • NaOH （ 0.0200mol•dm-3 confect fresh） • CH3COONa （ 0.0100mol•dm-3 confect fresh） • CH3COOC2H5（0.0200mol•dm-3 confect fresh）

  12. Apparatus and Reagent DDS-ⅡA Conductivity detector 1 Thermostatic trough 1 Bouble-tube conductance cell 2 Pipette (10ml) 2 Iodine flask 1 Stopping watch 1 NaOH （0.0100mol•dm-3confect fresh） NaOH （ 0.0200mol•dm-3 confectfresh ） CH3COONa （ 0.0100mol•dm-3 confectfresh ） CH3COOC2H5（0.0200mol•dm-3 confectfresh ）

  13. 1 2 3 average G0 G∞ Procedure 1.Adjust the temperature of thermostatic trough at 35℃. 2. Regulate the conductivity detector. Command theregulating technique. 3. Determine G0 and Gt (following the step which was said in page 73 of the teaching book.) Table 1

  14. 4.Determine Gt. (following the step which was said in page 74 of the teaching book.) Room temperature: Atmospheric pressure: The concentration of NaOH and NaAc solution are both 0.02M.

  15. Table 2

  16. Sketch-maps of Equipments

  17. Data Records and Processing 1、Finish the two tables above. 2、Draw a graph of against t, and calculate its slope Through the formula K = Slope/C figure out the value of K.

  18. Questions • 1.Why the experiment should be determined in constant temperature, CH3COOC2H5 and NaOH solution should be kept temperature constant before mixing. • 2.How to prove acetidin saponification is a second degrees reaction according to the results.

  19. Attentions • 1.Stuff up the stopper and make sure it wouldn’t leak out when blow NaOH to CH3COOC2H5 solution. • 2.Conductivity detector should be proofread for several times.

  20. Outline in the use of DDS-11A conductivity detector • 1. Switch on the electrical source and allow it warm-up for several min (until pointer turns stable). • 2. Turn the constant knob to be electrode constant (it’s been checked and determined by the factory).

  21. 3.Emendation. Determine conductivity of H2O on low round and HAc is on high round. Turn the knob, driving the pointer point to full scale namely ↗1.0. • 4.Determination. Choose proper measuring range from large range to small one and try to control the pointer pointing to the full scale in order to get accurate data. That just is: 104→103→102……10……1……0.1

  22. 5. Reading and record. The data marker is in the form of ×10x×10-6(s/cm). X stands for 4 , 3 or 2 and 1 in the measuring range.

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