Recall that a green band was left on the column. Why did that band remain on the column? What could you do in the procedure to elute that band?

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Experiment 13

Questions for Data Analysis and Results

1. Based on the structures shown in Figure 1, rank the four compounds in order of polarity (least polar to most polar). Then state the order of elution from the column (first to elute to last to elute).

2. Recall that a green band was left on the column. Why did that band remain on the column? What could you do in the procedure to elute that band?

3. How does the order of elution from a column relate to Rf values in TLC? (For example, does the first compound to elute from the column have the highest or lowest Rf value in TLC?)

4. Which of the four compounds shown in Figure 1 has the highest Rf value in TLC? Why? Which has the lowest Rf value in TLC? Why?

5. Were there likely additional compounds (besides one of the four listed in Figure 1) remaining on the column? How do you know?

 

How can it be explained that the reaction slower as time goes by? In other words, why does the slope of the concentration over time becomes smaller over time in a reaction? What kinetics does this indicate?

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Homework set 10 – Total points: 100

Instructions: Type your answers to the following questions and submit an electronic copy of your completed assignment on Canvas. Points for each question are indicated in front of the question. Name your file as CHEM151_HW10_FirstNameLastInitial

 

Question 1: Theoretical understanding of reaction kinetics (10pts)

After studying the slides, your notes from lecture and your readings, answer the following questions in 2-3 sentences for each part:

  1. Explain what reaction kinetics describe and how the study of kinetics is different from the study of a reaction at equilibrium.
  2. How does temperature affect reaction rates?
  3. How can it be explained that the reaction slower as time goes by? In other words, why does the slope of the concentration over time becomes smaller over time in a reaction? What kinetics does this indicate?
  4. Define the rate formula and the integrated reaction rate equation for zero and first order kinetics.
  5. The reaction between methanol and ethyl acetate is a reaction similar to the reactions involved in producing biodiesel. The reaction is first order with respect to methanol and zero order with respect to ethyl acetate. Write the reaction rate law for this reaction.

 

CH3OH + CH3CH2OCOCH3 ⟶ CH3OCOCH3+CH3CH2OH

 

Question 2 (5pts)

After doing the readings from section 20.1 of Van Loon and Duffy and/or the slides, answer the following questions in 2 sentences for each part:

  1. What is mineralization of organic compounds?
  2. True/False When an organic compound degrades the products are always less toxic
  3. Photolytic degradation of organic compounds: Under what conditions is it possible? What is required for such a reaction to occur?
  4. Indirect photolysis reactions can often be described by pseudo first order reaction. What is the reaction rate dependent on in such a case?
  5. Non photolytic reactions: what does it mean that a reaction is biotic versus an abiotic reaction? Give an example of a biotic reaction of an organic compound that you learned in this class (before Midterm 2).

 

Question 2 (5x5pts) Basic calculations of rates

  1. [11.24 – Dimensional analysis] Concentrations in atmospheric chemistry are most often reported in molecule/cm3. As a result, second-order rate constants used in modeling atmospheric chemistry are commonly reported in units of cm3 molecule–1 s–1. Convert the rate constants 3.5 x 10-14 cm3 molecule–1 s–1 to L mol–1 s–1. Is that unit conversion the same for all chemical compounds? What would you need to convert to L g-1 s-1?

 

 

  1. [11.27 – Dimensional analysis] Show that if the units of rate are mol L−1 s−1, then the units of the rate constant for the following second-order reaction are L mol−1 s−1:

 

H2(g) + Br2(g) à  2 HBr            rate = k [H2][Br2]

 

  1. [11.25 – Rate laws] For each of the rate laws below, what is the order of the reaction with respect to the hypothetical substances X, Y, and Z? What is the overall order?
    1. Rate = k[X][Y][Z]
    2. Rate = k[X]2[Y]1/2[Z]

 

  1. [11.29 – word problems to equations – rate laws]

The hypothetical reaction, A + B à C, has the rate law: Rate = k[A]x[B]y

When [A] is doubled and [B] is held constant, the rate doubles.

The rate increases fourfold when [B] is doubled and [A] is held constant.

What are the values of the exponents x and y?

  1. [11.32 – tabular data to equations – rate laws]

The following experimental data were obtained for the reaction

2 A + 3 B à C + 2 D

Determine the reaction order for each reactant and the value of the rate constant.

[A] (mol/L) [B] (mol/L) Rate = d[C]/dt (mol/L/s)
0.127 0.15 0.033
0.127 0.30 0.132
0.255 0.15 0.066

 

Question 3: Basic calculation of half-life for 1st order reactions (15 pts)

  1. The pesticide Carbaryl has a half life in soil of 19 days. Assuming its degradation follows first order kinetics, calculate the reaction constant. Then, write the kinetics equation as a rate law and as an integrated law.

 

  1. The pesticide Heptachlor has a reaction 0.006 /day. Assuming its degradation follows first order kinetics, calculate the half-life of heptachlor and interpret its meaning.

 

  1. The concentration of a chemical was measured at 15 mg/L. 20 hours later it was measured at 10 mg/L. Assuming the chemical degrades with first order kinetics, what is the reaction rate of the chemical and its half-life?

 

Question 4: Using the equation for first order kinetics – exponents/logarithms practice (15pts)

Consider dieldrin, a pesticide in the category of organochlorines. It has a half-life of 934 days. After calculating its reaction rate constant, assuming first order kinetics, calculate the following:

  1. For an initial concentration of 12 ppm in water, calculate the concentration after 10 hours, after 1 month, and after 1 year.
  2. Considering a water that has 40 ppb of dieldrin in it, how long will it take for the concentration to drop below 5 ppb.
  3. How long will it take for the concentration to reach 10% of its initial value, regardless of the starting concentration.

 

Question 5 – Determining order of reaction and reaction rate from exp data (10pts)

[EXCEL NEEDED] A new organic compound is tested to determine its kinetics and reaction rate. Concentrations of the chemical were measured under the same conditions for 50 hours, starting at a concentration of 14 ppm. The data from the experiment is given below:

time (hr) C (ppm)
0 14
5 10.03
10 6.85
15 5.3
20 3.47
25 1.9
30 1.71
35 0.76
40 1.1
45 0.27
50 0.29

 

  1. Is the degradation of the compound following zero or first order kinetics? Use an appropriate quantitative metric to justify your answer.
  2. Assuming first order kinetics, determine the reaction rate of the compound by linearizing the integrated rate law for first order kinetics and determine the first order reaction rate and the corresponding half-life.

Question 6 [11.49] Determining order of reaction and reaction rate from exp data (15pts)

[EXCEL NEEDED] The rate of photodecomposition of the herbicide picloram in aqueous systems was determined by exposure to sunlight for a number of days. One such experiment produced the following results, (Data from Hedlund, R.T., Youngston, CR. “The Rates of Photodecomposition of Picloram in Aqueous Systems,” Fate of Organic Pesticides in the Aquatic Environment, Advances in Chemistry Series, #111, American Chemical Society, (1972), 159–172.)

  1. Determine the order of the reaction that best fits this data by checking if the best model is zero, first or second order kinetics.
  2. Then for the best model, determine the rate constant, and the half-life for the photodecomposition of picloram.

 

time (days) C (umol L-1)
0 4.14
7 3.70
14 3.31
21 2.94
28 2.61
35 2.30
42 2.05
49 1.82
56 1.65

 

 

Question 7 [11.57] – Arrhenius relationship for k dependence on temperature (5pts)

[EXCEL NEEDED] The table below presents rate constants measured at three temperatures for the following reaction, which is involved in the production of nitrogen oxides in internal combustion engines.

 O(g) + N2(g) à  NO(g) + N(g)

 

Determine the activation energy of the reaction in kJ/mol.

k (L/mol/s) Temperature (K)
4.4E02 2000
2.5E05 3000
5.9E06 4000

 

State the reaction that was done, how the product was purified, and how the product was analyzed. State the percent yield. Draw the overall reaction (not the mechanism).

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Organic Chem Formal Lab Report/ Worksheet

State the reaction that was done, how the product was purified, and how the product was analyzed. State the percent yield.

Draw the overall reaction (not the mechanism). You must come up with the drawing yourself (by hand or electronically). Do not copy it from anywhere.

 

Summarize the chemical hazards.

Write a formal procedure for this experiment based on what you did in lab, using your values (initial and final masses, etc.). The balances had 4 decimal places, so should your values, and they should match the numbers you wrote in your notebook from your observations. If they do not match, points will be deducted.

Show your calculations for theoretical and percent yield based on your values from lab.

List IR peaks, assign them, and state the significance of them. Discuss any significant peaks missing (compare starting material and product). Attach your IR.

 

Discussion:

Discuss the mechanism of this reaction, how the product was purified, and any factors that would impact your percent yield. Discuss the purity of your product based on IR. Based on your results, suggest any changes that should be made in the future to improve the yield and/or purity. Include one peer-reviewed source somewhere in your discussion. Cite it using ACS style.

Read the attached paper and write a summary on it as per requirements mentioned here.

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Cheminformatics

  • https://www.studypool.com/questions/download?id=2833537&path=uploads/questions/2518174/20230503214356chemical_representations.pdf&fileDownloadName=attachment_1

Read the attached paper and write a summary on it as per requirements mentioned here.

Style:

Reading assignments should be 12 point font and single spaced. The paper summary should contain no headings and should be no less than ½ a page and no more than 1 page in length. There should be no spacing between paragraphs.

Format:

The language should be written in a professional, academic manner and should read like scientific correspondence (e.g., in the style of a journal article). For example, submissions should be written in third person. Paragraphs must have a clear and logical organization. They should stick to one topic and be ordered in a logic manner to flow with the paper. In general, you should have at least one paragraph introducing the main topic of the paper and providing necessary background, one or more paragraphs summarizing the main concepts from the paper, and a one paragraph conclusion.

In a spontaneous electrochemical cell, at which electrode does reduction occur? In a spontaneous electrochemical cell, at which electrode does oxidation occur?

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Exercise 10 Report Form:  Electrochemistry – Galvanic Electrochemical Cells

 

Name: _________________________________         Date:  ____________________

Lab Partner: _____________________________        Instructor: ________________

 

Electrochemical cells:

Reaction Zn + Cu2+ (0.10 M) ® Zn2+ (0.10 M) + Cu Zn + Fe2+ (0.20 M) ® Zn2+ (0.10 M) + Fe Fe + Cu2+ (0.10 M) ® Fe2+ (0.20 M) + Cu Zn + Br2 (sat’d) ® Zn2+ (0.10 M) + 2 Br– (0.5 M) Cu + Cu2+ (0.10 M) ® Cu2+ (1.0×10-5 M) + Cu
(2 points) Measured potential (V)          
(2 points) Calculated potential (V)          
(2 points) Which substance is oxidized?          
(2 points) Which substance acts as the cathode?          
(1 point) The e– flow from which electrode?          
(1 point) The e– flow to which electrode?          

 

  1. (1 point) In a spontaneous electrochemical cell, at which electrode does reduction occur?
  2. (1 point) In a spontaneous electrochemical cell, at which electrode does oxidation occur?
  3. (1 point) In a spontaneous electrochemical cell, electrons flow from which electrode to which electrode?
  4. (2 points) For full credit, show your calculation of the ‘Calculated Potential’ for the Cu/Cu concentration cell.

 

 

 

Given in each item is a reaction scheme showing the reactant/s, reagent/s, and major product. If the compound shown at the right side is not the major product, rewrite the scheme to show the correct product/s.

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Chemistry Question

INSTRUCTIONS
– Given in each item is a reaction scheme showing the reactant/s, reagent/s, and major product. If the compound shown at the right side is not the major product, rewrite the scheme to show the correct product/s.
– Propose a feasible mechanism for each reaction.
– Observe the proper construction of reaction mechanisms (arrow positioning, types of arrow heads, lone pair electrons, charges, entry/exit of chemical species, etc.). You may also provide a brief explanation (NMT 5 sentences) for your answer.
– Stereoselectivity and regioselectivity of reactions must be observed, whenever applicable. Show the stereochemistry of the compounds using solid– and hashed–wedged bonds. Incorrect isomers will not be considered.

Solute A has a K = 2.5 for an extraction between water (phase 1) and chloroform (phase 2). If 100 mL of a 0.01M solution containing A in water is extracted one time with 400 mL chloroform, what fraction will be extracted? For the same solute, what fraction will be extracted if 5 extractions with 80 mL chloroform each are used (instead of one 400 mL extraction)?

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Analytical Chemistry 2

HW #3 for Chem 318      Due: May 1, 2023

  1. Solute A has a K = 2.5 for an extraction between water (phase 1) and chloroform (phase 2). If 100 mL of a 0.01M solution containing A in water is extracted one time with 400 mL chloroform, what fraction will be extracted? For the same solute, what fraction will be extracted if 5 extractions with 80 mL chloroform each are used (instead of one 400 mL extraction)?
  2. A solute is separated on a column (length: 25 cm) with a peak at 25.5 minutes (retention time) and the baseline peak width of 0.7 minutes. Calculate the number of theoretical plates and the theoretical plate height of this column.
  3. Two compounds (compound 1 and compound 2) are separated on a column with retention time being 14.6 minutes and 16.8 minutes, respectively. The baseline peak width of the two peaks is 0.8 minutes and 1.0 minutes, respectively. Are these two compounds separated completely? Why or why not?
  4. Describe the factors that contribute to the chromatographic peak broadening (hint: Why bands spread?).
  5. List the types of liquid chromatography (categorized based on separation principles) and briefly describe the principles used for separation for each type.
  6. What are the desirable properties for the immobilized liquid stationary phase in a gas-liquid chromatographic column?
  7. What characteristics does an ideal detector for gas chromatography have?
  8. Briefly describe the principle of operation for the following gas chromatographic detectors: 1).Flame Ionization Detector (FID); 2).Thermal Conductivity Detector (TCD); 3).Electron-Capture Detector (ECD).
  9. What advantages does HPLC possess vs GC?
  10. List the components of an HPLC instrument.
  11. Briefly describe the principle of operation for the following HPLC detectors: 1).UV absorbance detector; 2).Fluorescence detector; 3).Refractive-index detector; 4).Electrochemical detector; 5).Mass spectrometric detector. (In addition to going through the slides, you may need to read the textbook and other reference books to finish this question).

 

 

Draw these two reactants and then show a full arrow-pushing mechanism providing the flow of electrons, showing how the two react with one another and the resulting product.

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Chemical reaction in solution

Part I: Mechanisms (20 points). Reaction A: consider a solution of acetophenone (AKA methyl phenyl ketone) and sodium trifluoroperacetate (deprotonated trifluoroperacetic acid). Draw these two reactants and then show a full arrow-pushing mechanism providing the flow of electrons, showing how the two react with one another and the resulting product.

Which material seems to be unaffected by the temperature of the water? Which material is most greatly affected by the temperature of the water?

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Solubility Curves

Using the following graph to answer the questions.

1) Which material seems to be unaffected by the temperature of the water?

2) Which material is most greatly affected by the temperature of the water?

3a) Which material dissolves the most in 15OC water?  b) Which material dissolves the least?

4) At what temperature of water will the water dissolve more KClO3 than HCl?

5) How many more grams of HCl can be dissolved in 100 g of water at 60 OC than SO2 at the same temperature?

6) What kind of solution would be present if 55 grams of NH3 were dissolved in 100 g of water at 35 OC?

7) What is the maximum mass of KNO3 that can be dissolved in 100 g of water at 75 OC?

8) How many grams of NH4Cl can dissolve in 500 g of water at 25 OC?

9) How many grams of KClO3 can dissolve in 10 g of water at 25 OC?

How many fathers were scientists or had an educational background?

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History of Chemistry

Look at Jeannette Brown’s books 1 and 2.

Have a slide talking about the statistics of Father’s Influences

  • How many fathers were scientists or had an educational background?

Examples of how they were influenced.

Have a good amount of people (3-4 people)