Unit Operations Lab I (CHEGR3787L)
August 27, 2004
1) Using method of excess reactants confirm that the saponification of ethyl acetate is first order with respect to NaOH.
2) Confirm that the reaction is first order with respect to NaOH and ethyl acetate
a. Run experiments with different starting concentration ofNaOH and ethyl acetate. Using the rate of zero time and conduct a least squares analysis (page 209 of Fogler)
b. Compare the concentration versus time data obtained from the experiment to the curve predicted by the supplied excel sheet
3) Determine the activation energy of the reaction and compare to the literature value
Researchers typically use a batch reactor tostudy reaction kinetics under ideal conditions. A batch reactor can be used to find the reaction rate constant, activation energy and order of the reaction. The use of a batch reactor for the most part eliminates the effects due to fluid flow on the resulting reaction rates. Consequently, the data reflect the intrinsic kinetics for the reaction being investigated.
Your goal for this experimentis to find the kinetics for a liquid-phase (mildly exothermic) irreversible reaction. The reaction chosen for the experiment is given below
This reaction is first order with respect to NaOH and ethyl acetate. You will determine if your experimental data confirms the order of the reaction and the activation energy. You will use two probes to measure the extent ofreaction. Procedure to use the two probes described later.
Conductivity and pH probes would be used during the experiment to determine the extent of reaction.
Conductivity probe measure the conductivity of the solution. In the present experiment, sodium hydroxide and sodium acetate would contribute to the conductivity of the solution. Let k0 be conductivity ofthe solution at the start of the reaction. At the start, only sodium hydroxide would contribute to the conductivity. As reaction proceeds, sodium acetate starts forming after consumption of sodium hydroxide resulting in different conductivity results. The consumption of NaOH can be found using the following relationship
C(t) = Concentration of NaOH at time tCA0= Initial concentration of NaOH
[pic]= Conductivity of solution at time t
[pic]= Initial conductivity of solution
[pic]=Conductivity at the end of reaction
The conductivity contribution due to sodium hydroxide is different from the contribution due to sodium acetate. So one has to find for [pic] each reaction run.
The pH probe measures the pH of the solution. The pH of thesolution is directly related to the amount of OH ions present in the solution. . The formulas needed to calculate the concentration of [OH]- from pH is given below:
For example, if pH = 12 means [OH]- = 0.01 M
Note: the value of 14 is valid only for 25(C temperature. This value changes with change in the reaction temperature. Use the appropriate value for the experimentaltemperature.
Tasks and Questions for each week
Answers to the question should be submitted at that start of the class for that week. For example, answers to week 1 questions should be submitted at the start of week 1 experiments. Failure to submit answers in a timely fashion would affect the 50 points for answers and sample calculation part of the grade for the report.
Week 11) Describe how do you find order of a reactant using the method of excess reactants? Give the graph that would be used to prove that the reaction is first order with respect to NaOH. Use differential method of analysis
2) Find a relation of Kw as a function of temperature. Kw gives the value for pH + pOH for a given temperature.
3) What is the weight of NaOH to be added to 1.5 liters...