Experiment 9 Student Report Template PDF

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REPORT COVER SHEET AND DECLARATION School of Chemistry The University of Melbourne Laboratory Report Cover Sheet Student Name: Student Number: Subject Name & Code: Demonstrator: Experiment Title:

Experiment 9: Rates of Reaction: The Hydrolysis of t-Butyl Chloride

Due Date: _____________________________ By submitting work for assessment, I hereby declare that I understand the University’s policy on academic integrity and I declare that: • This laboratory report is my own original work and does not involve plagiarism or unauthorised collusion, except where due credit is given to the work of others. The report is based on results

and spectra obtained by me during my laboratory session. • This laboratory report has not previously been submitted for assessment in this or any other subject. For the purposes of assessment, I give the assessor of this assignment the permission to: • Reproduce this laboratory report and provide a copy to another member of staff; and • Take steps to authenticate the assignment/laboratory report, including communicating a copy of this assignment to a checking service (which may retain a copy of the assignment on its database for future plagiarism checking). Feedback on Report: Feedback on your report and the mark you received will be available on the Online Practical Assignments page on Canvas. Plagiarism: Plagiarism is the act of representing as one's own original work the creative works of another, without appropriate acknowledgment of the author or source. Collusion: Collusion is the presentation by a student of an assignment as his or her own work, but which is in fact the result in whole or in part of unauthorised collaboration with another person or persons. Collusion involves the cooperation of two or more students in plagiarism or other forms of academic misconduct. Both collusion and plagiarism can even occur in group work. For examples of plagiarism, collusion and academic misconduct in group work please see the University’s policy on Academic Honesty and Plagiarism: https://academichonesty.unimelb.edu.au Plagiarism and collusion constitute cheating. Disciplinary action will be taken against students who engage in plagiarism and collusion as outlined in University policy. Proven involvement in plagiarism or collusion may be recorded on your academic file in accordance with Statute 13.1.18.

Experiment 9: Rates of Reaction: The Hydrolysis of t-Butyl Chloride Author(s): Day/Time/Group number: Abstract: (Summary of what you did and what you found out)

Through hydrolysis of t-BuCl (equation) and measuring its conductivity against conductivity of infinity solution at different temperatures, the rate constant is determined by measuring the gradient of the ln (Kinf – Kt) vs time. This produced a rate constant of – for 0.5 and – for 38 and suggested that a higher temperature resulted in a greater rate constant and reaction rate. Then by comparing the rate constant for 0.5, 25,30,35,58 in a ln(k) vs 1/T graph, the gradient was used to calculate the activation energy required for the reaction to start which was ---.

Introduction and Aim: (What is this type of reaction called in organic chemistry, what mechanism would you predict, what information can you get from kinetics about the mechanism what are you trying to find out in this experiment?) The aim of this experiment is to determine the reaction rate of the hydrolysis of t-BuCl at different temperatures and the activation energy required to start the reaction. This type of reaction is called nucleophilic substitution reaction and its mechanism is SN1. In SN1 reactions, its rate of reaction is dependent on the concentration of the reactant and thus is a first order reaction.

Experimental: (How did you perform your experiment?)

Results: (Tables of data)

Conductance data for hydrolysis of t-butyl chloride at various temperatures Graphing data 1. For the data at each temperature (0.5 °C and 38 °C), use your  and the successive t value to plot ln( − t) against time (in seconds). You should construct separate graphs for each temperature (the scales should be different). This will provide more precise results for your rate constant determination. (2 graphs) 2. Draw the line of best fit through your calculated data points. 3. If your graph deviates significantly from linearity, exclude measurements which deviate from linearity and draw a line of best fit. If you do so, include BOTH graphs, before and after excluding points, with the R2 values. 4. Determine the gradient of the line of best fit you have drawn for the graph in Step 3 (include units). 5. Determine the first-order rate constant (k) from the gradient of your graph at 0.50C and 38oC, and enter values in Table 3. For good graphing technique, using Excel: • label axes with correct scales and units • include a title • draw the line of best fit • show equation of line and R2value

1. Hydrolysis run at 0.5 °C The conductance measurements for a kinetics run carried out at a temperature of 0.5 °C is given in Table 1. Use this data to determine the rate constant k at 0.5 °C. This value of the rate constant will be used in your estimate of the activation energy for the reaction.

Table 1: Data for hydrolysis run at temperature = 0.5 °C ( for this experiment is 80.00 μS/cm) Time (sec)

t (μS/cm)

0

2.99

360

3.75

720

4.59

900

4.96

1200

5.63

1800

6.96

2400

8.26

3000

9.54

3600

10.73

Graph:

Equation of the line……………………………………………. R 2 value…………………………………………………………….. k, rate constant at 0.5oC………………………………………

  −  t (μS/cm)

ln( − t

2. Hydrolysis run at Temperature = (note temperature HERE) The conductance measurements for a kinetics run is given in Table 2. Use this data to determine the rate constant k at this temperature. This value of the rate constant will be used in your estimate of the activation energy for the reaction.

(  for this is RECORD THE HERE

Table 2: Data for hydrolysis run at temperature = ….(Record temp here) experiment t − t Time μS/cm).   −  ln(  t  (sec) (μS/cm) (μS/cm) VALUE OF  120 180 240 300 360 420 480 540 600 660 720 780 840 900 960 1080 1200 1320 1440 1560 1680 1800

Graph:

Equation of the line………………………………………………….. R 2 value……………………………………………………………………. k, rate constant at ………..(record temp. here)……………………………..

3. Rate constants measured at five different temperatures will be used in the determination of activation energy (Ea, equation 9.8) for the t-BuCl hydrolysis reaction.

This includes the rate constant derived from the analysis of the temperature = 0.5 °C and your experimental data; there should be values for rate constants at 25 °C, 30 °C, 35 °C and 38 °C (either class data in F2F or provided by your demonstrator in Online classes). 1.

Calculate ln(k(T)) and 1/T (K-1) for all kinetic runs.

2.

Plot ln(k(T)) and 1/T data pairs from Table 3; if there are 2 values at a particular temperature then plot both values.

T ( oC)

0.5 25 25 30

30 35 35

38 38

T (K)

1/T (K-1)

k, rate constant (s-1)

ln(k)

Table 3. Rate constants at various temperatures for the hydrolysis of t-BuCl.

Graph:

Equation of the line……………………………………… R 2 value………………………………………………………. Gradient ………………………………………………. (this data will be used in Question 6 below)

DISCUSSION REMEMBER THAT ANSWERS NEED TO BE SUPPORTED BY EVIDENCE FROM YOUR DATA OR THEORY Question 1 Which species in the reaction scheme for the hydrolysis contribute to the conductivity of the solution and why?

Question 2 Inspect the two sets of data provided, at 0.50C and 38oC. How does the reaction rate vary with temperature? (What is the experimental evidence for your answer.)

Question 3 Look at the measured conductivity values for the kinetic run at 0.5 oC. Why is there a difference between the conductivity of the infinity solution, and the conductivity measurement at t=3600 s? (Think about rates and temperatures and extent of reaction.)

Question 4 This hydrolysis reaction is a first order reaction, therefore rate = k[tBuCl]. i. What is the expected effect on the rate when the concentration is tripled? Show mathematically.

ii.Given the following rate law, rate = k[A]1[B]x, when the concentration of A is doubled and the concentration of B is doubled, the rate is observed to increase by a factor of 8. What is x, the order of reaction with respect to B? Show mathematically.

Reaction half-life (t½) Question 5 a) What is the relationship between the rate constant k for a first order reaction and halflife (t½)?

b) Calculate the half-life for the reaction at: (i) 0.5 °C

and

(ii) 38.0 °C.

Show working.

Question 6 Activation energy derivation What is the activation energy for this reaction? (show all working) (Derive the activation energy including correct units from the determined gradient of the plot of values in Table 3, using Equation 9.9 from the Student Notes (R = 8.314 J mol -1K-1))

Conclusion: (What have you found out?)...