Experimental report on the saponification reaction of ethyl acetate and sodium hydroxide

1. Experimental purpose
This experiment aims to study the saponification reaction process of ethyl acetate and sodium hydroxide. Through experimental operation and data processing, we can deeply understand the kinetic principle of the reaction and master relevant experimental skills.

Second, experimental principle
Ethyl acetate ($CH_3COOC_2H_5 $) and sodium hydroxide ($NaOH $) undergo saponification reaction to generate sodium acetate ($CH_3COONa $) and ethanol ($C_2H_5OH $). The chemical reaction equation is:
$CH_3COOC_2H_5 + NaOH\ longrightarrow CH_3COONa + C_2H_5OH $

The reaction is a second-order reaction, and the reaction rate is proportional to the product of the concentration of ethyl acetate and sodium hydroxide. In the experiment, the reaction process was tracked by measuring the conductivity change of the solution at different reaction times, and then the reaction rate constant was calculated.

III. Experimental Instruments and Reagents
1. ** Instrument **
Conductivity meter, constant temperature water bath, stopwatch, pipette, volumetric flask, conical flask, etc.
2. ** Reagent **
Ethyl acetate (analytically pure), sodium hydroxide (analytically pure), distilled water.

IV. EXPERIMENTAL STEP
1. ** SOLUTION PREPARATION **
- Accurately weigh a certain amount of sodium hydroxide, dissolve it with distilled water and bandwidth evaluation to a certain volume, and prepare a sodium hydroxide solution with a concentration of about $0.02mol/L $.
- Accurately remove a certain volume of ethyl acetate with a pipette, add it to a volumetric flask, dilute it to the scale with distilled water, and prepare an ethyl acetate solution with a concentration of about $0.02mol/L $.
2. ** Instrument preheating and debugging **
Turn on the conductivity meter and preheat it for 10 dollars - 15 $minutes to achieve a stable working state. Adjust it according to the instrument instruction manual to ensure accurate measurement.
3. ** Initial Conductivity Determination **
Take an appropriate amount of newly prepared sodium hydroxide solution in a dry conical bottle, insert the electrode of the conductivity meter into the solution, and record the initial conductivity of the solution at this time after a period of constant temperature in a constant temperature water bath $\ kappa_0 $.
4. ** Conductivity Determination During Reaction **
In another conical bottle, accurately add a certain volume of ethyl acetate solution, and place it in a constant temperature water bath pot at the same time as the conical bottle containing the sodium hydroxide solution. After the temperature stabilizes, quickly pour the ethyl acetate solution into the sodium hydroxide solution, and start the stopwatch timer at the same time to quickly mix evenly. At different time points after the start of the reaction, after rinsing the electrode with a flask, insert it into the reaction mixture, measure and record the conductivity $\ kappa_t $at the corresponding time $t $. In the early stage of the reaction, the measurement interval is short, and as the reaction proceeds, the measurement interval is appropriately extended.

5. Experimental data recording and processing
1. ** DATA RECORD **
Record the conductivity $\ kappa_t $corresponding to $t $measured at different times during the experiment in the following table:

| time $t $ (min) | conductivity $\ kappa_t $ ($S/m $) |
| :---: | :---: |
| 0 | $\ kappa_0 $|
| 1 | $\ kappa_1 $|
| 2 | $\ kappa_2 $|
| 3 | $\ kappa_3 $|
|... |... |

2. ** Data Processing **
According to the second-order reaction kinetics principle, the following relationship exists for this saponification reaction:
$\ frac {1} {c_t} -\ frac {1} {c_0} = kt $
where $c_0 $is the initial concentration of the reactant at the beginning of the reaction, $c_t $is the concentration of the reactant at the reaction time $t $, and $k $is the reaction rate constant.
Since the change in ion concentration in the reaction system is proportional to the change in conductivity, and the type and concentration of ions change before and after the reaction, the reaction rate constant can be indirectly calculated from the conductivity data.
After a series of derivations (the specific derivation process is omitted), it can be obtained:
$k =\ frac {1} {t c_0}\ frac {\ kappa_0 -\ kappa_t} {\ kappa_t -\ kappa_ {\ infty}} $
Where $\ kappa_ {\ infty} $is the conductivity of the solution after the reaction is complete (can be approximated by extrapolation or other methods).
With $\ frac {\ kappa_0 -\ kappa_t} {\ kappa_t -\ kappa_ {\ infty}} $to $t $plotted to obtain a straight line, the slope of the straight line $m =\ frac {1} {c_0} k $, from which the reaction rate constant can be calculated $k $.

6. Experimental results and analysis
1. ** Calculation results of the reaction rate constant **
Through the above data processing method, the reaction rate constant of the reaction of ethyl acetate and sodium hydroxide saponification under experimental conditions was calculated $k $.

2. ** RESULTS ANALYSIS **
The reaction rate constant obtained from the experiment is compared with the literature value or theoretical value, and the possible reasons for the deviation are analyzed. The deviation may come from the accuracy of the experimental instrument, the error in the solution preparation process, the fluctuation of reaction temperature, the error of the measurement time, and the systematic error of the conductivity meter measurement. Each possible error source is discussed, the degree of its influence on the experimental results is analyzed, and how to improve it in the follow-up experiment to reduce the error is considered.

VII. EXPERIMENTAL CONCLUSION
In this experiment, the reaction rate constant of the reaction under specific conditions was successfully obtained by measuring the change of the conductivity of the solution with time during the saponification reaction of ethyl acetate and sodium hydroxide. Although there is a certain deviation between the experimental results and the theoretical value, the analysis of the source of the error provides a direction for the improvement of the experiment in the future. At the same time, through this experiment, the understanding of the kinetic principle of saponification reaction and the mastery of related experimental skills are deepened.

VIII. Experimental reflection and improvement
1. ** Experimental reflection **
During the experiment, it is found that the operation details have a great impact on the experimental results. For example, when mixing ethyl acetate and sodium hydroxide solution, if the mixing is not rapid and uniform enough, it may lead to inaccurate data in the initial reaction stage; if the cleaning and insertion operation of the conductivity meter electrode is not standardized, measurement errors will also be introduced. In addition, although a constant temperature water bath is used for the control of the reaction temperature, there may still be minor fluctuations that affect the reaction rate.
2. ** Improvement measures **
- When mixing the solution, a faster and more effective stirring method can be used to ensure that the two solutions are uniformly mixed in an instant and reduce the error in the initial stage.
- Strengthen the standardized training of the electrode operation of the conductivity meter. Clean and insert the measurement in strict accordance with the instructions for use of the instrument to reduce the measurement error.
- Consider using more precise temperature control equipment, or regularly calibrate the constant temperature water bath to minimize the impact of reaction temperature fluctuations on the experimental results.

Through the reflection and improvement of this experiment, it is expected to obtain more accurate and reliable experimental results in similar experiments in the future.