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Spring 2015 CHEM 220 Lab
Introduction to
Quantitative Chemical Analysis
Dr. Audra Goach Sostarecz
Chemistry Laboratory Rules
In order to participate in any Monmouth College chemistry laboratory course you are required to read and understand these laboratory rules. If you agree to follow the rules as stated in this document, please sign and print your name on the “sign-in” sheet.
(1) Safety glasses are required in the laboratory at all times. Wearing contact lenses in a chemistry laboratory can be harmful to your eyes. Contact lenses should be replaced by prescription glasses except in rare cases when it is not possible. The wearing of contact lenses in the laboratory is discouraged. If you accidentally get a chemical in your eyes, wash the eye with flowing water from the sink or eye wash fountain for 15-20 minutes, report the incident to the instructor and seek professional medical attention immediately.
(2) In case of fire or accident, notify the instructor or laboratory assistant at once. Note the location of fire extinguishers, fire blankets, safety showers, and eye wash fountains so that you can use them if needed.
(3) Report all types of accidents, chemical spills, cuts, burns, or inhalation of fumes to the lab instructor. Clean up chemical spills immediately. First aid and/or transportation to the hospital emergency room will be arranged.
(4) Long hair must be securely confined when in the laboratory. Be aware that some clothing is especially flammable or subject to chemical attack. Do not sit or place valuables on laboratory benches. Backpacks should be left in the designated area.
(5) Eating, drinking, smoking, gum chewing or application of cosmetics in areas where chemicals are present is forbidden. Water bottles and other beverage containers are not allowed in the lab.
(6) Remove gloves and wash hands carefully before leaving the laboratory. When wearing gloves, be careful not to contaminate your clothing, pens or pencils, door knobs, drawer handles, balances, etc.
(7) Cell phones, ipods and other personal devices are not to be used in the laboratory.
(8) All chemical and hazardous wastes must be disposed of safely in the proper waste container. Any violation of this rule is a serious safety and environmental concern and will affect your grade.
(9) Each lab section should be clean before leaving the lab. This includes balance areas, regent shelves, lab desktops, and your personal glassware/equipment. Failure to keep your lab section clean will affect your grade.
(10) Exercise great care in observing odors and perform experiments creating fumes in the ventilated hoods.
(11) Do not take any chemicals, unknowns, or equipment out of the laboratory.
(12) Do not use mouth suction to fill pipettes; use the suction bulbs provided.
(13) Do not force glass tubing or thermometers into rubber stoppers. Use a lubricant (glycerine or water) and protect your hands with a towel when inserting tubing into or removing it from a stopper. Place any broken glass in the container provided, not in the trash.
(14) Sturdy, closed (not open-toed) shoes must be worn in the lab. Sandals, flip-flops and perforated shoes are not permitted.
(15) Shorts, skirts and tank tops must not be worn in the lab.
(16) When working with electrical equipment, make sure wires are properly insulated; if not please discontinue use and report the problem to the instructor.
(17) Never perform unauthorized experiments.
(18) Never work in the laboratory alone.
(19) I understand that by refusing to follow the above rules I may be asked to leave the lab and my laboratory grade in this course may be affected.
SPRING 2015 CHEM 220
Introduction to Analytical Chemistry with Lab
Syllabus
Instructor: Dr. Audra Goach Sostarecz Office Hours: 11:00am – 12:00pm M,F
356 CSB 2:00pm – 3:00pm W
309-457-2252 - office 12:00pm – 1:00pm R
309-221-9432 – cell others by appointment
asostarecz@monm.edu
CHEM 220_01 Lecture: MWF 12:00-12:50pm; CSB 378
CHEM 220_02 Lecture: MWF 1:00-1:50pm; CSB 378
Lab: Tues(01) or Thurs(02), 1:00-4:50pm; CSB 370; meet in CSB 380
Required Textbook: Quantitative Chemical Analysis, 7th Edition, Daniel C. Harris
Required Readings and Handouts: TBA on webpage
Required Supplies: Basic Calculator – ***Cell phones, iPods, or iPads are NOT to be used as calculators
Grading for Lecture Exam Dates:
|Exams |60% | |January 28 |
|Quizzes/Homework |20% | |February 20 |
|Final |20% | |April 1 |
| | | |April 24 |
|FINAL EXAM: 8am; Friday, May 8 (Multiple Section Time) |
Grading for Lab
|Report Sheets/Lab Reports |50% |
|Lab Notebook |10% |
|Journal Articles /Quizzes/Homework |25% |
|Final Group Presentation |15% |
Overall Grade: Your total lab grade will comprise 25% of your course grade. However, you cannot successfully pass the course with a C- if your lecture grade is lower than a C-.
Letter Grades: A [pic] 93 [pic] A− [pic] 90 [pic] B+ [pic] 87 [pic] B [pic] 83 [pic] B− [pic] 80 [pic] C+ [pic] 77
77 [pic]C [pic] 73 [pic] C− [pic] 70 [pic] D+ [pic] 67 [pic] D [pic] 63 [pic] D− [pic] 60 [pic] F [pic] 0
Hours per Week Work Expectations: I will expect that you dedicate to this course at least the hours indicated below. These are predetermined weekly averages. Obviously, the hours per week could fluctuate if, for example, you have a lab report due and an exam in one week.
|Class Lectures |2.5 |
|Reading/Homework |2.0 |
|Quizzes/Exams/Final - preparation for |1.5 |
|Lab Lecture and Lab |4.0 |
|Lab Report Sheets/Lab Reports |2.0 |
|Lab Notebook |0.5 |
|Lab Journal Articles/Quizzes/Homework |1.0 |
|Lab Final Group Presentation – preparation of |0.5 |
|Total Hours per Week* |14 |
*This is the average amount of time that a student needs to spend per week to complete the coursework.
Lecture Goals: This class will provide you with an understanding of both the qualitative and quantitative nature of chemical analysis. You will be provided with extensive exposure to the principles of chemical equilibrium, titrations, and buffers in lecture and homework problems. You will also develop an appreciation for analytical methods and instrumental methods, including Spectroscopy and Electrochemistry that have emerged out of the field of Analytical Chemistry and are now currently used in a vast number of scientific fields. By doing all of the above, you will, most importantly, develop critical thinking skills which you will use throughout your college and life career.
Lab Goals: In this lab, you will develop the necessary skills to solve analytical problems quantitatively while at the same time honing your analytical skills in the laboratory. You will be asked to judge your laboratory technique by the precision and/or accuracy of your experimental data. You will also develop a sense for the vast use of the principles of Analytical Chemistry in the sciences. This lab meets for 4 hours a week allowing us to spend at least on hour in lecture each week. Much of this lecture time of the lab will also be spent on developing scientific writing skills.
Attendance: Any more than 3 unexcused absences in lecture or more than 1 unexcused absence in lab will result in you failing this course. If an incident that will require you to miss a class and/or lab arises, please contact me by email, phone, or an office visit before class or lab begins. I will then decide whether this is an excused absence or not. All assignments will be posted on my webpage. Regardless if your absence is excused or not, you will be held responsible for all material covered in your absence, and you will be required to complete any work missed within a reasonable amount of time.
Participation: Class participation will help determine borderline grades. NO use of electronic media in class such as cell phones, iPods, iPads, and computers unless told otherwise.
Lecture Exams: Four 50 minute exams will be given during the semester. Unexcused absences on any exam will count as a zero. For an excused absence, you need to contact me (phone or office visit) before the exam begins.
Lecture Quizzes/HW: Quizzes are given in order to keep you up to date on the material. You will be quizzed on the HW and lecture material. Quiz dates are preset in your class schedule. HW problem sets will also be collected periodically.
Lecture Final Exam: The final is scheduled for Fri, May 9 at 8am (Multiple Section Time). Please see me early if you have a conflict.
Lab Safety: Safety goggles, closed-toed shoes, and long pants must be worn in the lab at all times. See lab safety guidelines in your lab manual for a more extensive list of safety rules.
Lab Reports: Lab reports will be graded for format, clarity of writing, content, and statistical data analysis. A general format for the lab reports will be given to you before the first lab is due.**Lab report due dates are preset. For each day that your lab report is late, you will lose a half-letter grade.
Lab Report Sheets: The report sheets will be graded for each lab. The due date for each report sheet is preset and listed on your lab schedule. For each day that your report sheet is late, you will lose a half-letter grade. You will not receive a lab report sheet grade until you complete the data correctly. This will result in a 0% on the report sheet until the correct work is received.
Lab Notebook: Lab notebooks from Gen Chem may be used or carbonless lab notebooks can be purchased at any office supply store. Copies of notebook pages will be collected before and after each lab and checked for the following information: pre-lab material, calculations, notes, and conclusions. ALWAYS keep your notebook current – it is to your benefit as a scientist! Lab Notebook guidelines are given in your lab experiment packet.
Lab Journal Articles: For some of the labs, you will be asked to download and print out an ACS journal article () that relates, in some manner, to the current lab that you are doing. You will need to write a short summary/critique of the article which you may be asked to share with the class.
Lab Quizzes/Homework: Quizzes and homework will consist of lab information and/or assigned problems.
Lab Group Presentation: For the last lab which will be designed by you, you will be asked to present your results in the form of a presentation on the day that your final is scheduled (Wednesday, May 13 at 3pm). You will work in groups for this lab. EVERYONE must contribute to the presentation as grades will be assigned individually.
Lab Conduct: When working in the lab, please be aware of your surroundings. ALWAYS use the hoods or snorkels when assigned to do so. Not abiding by the rules may result in serious injury in this lab due to our heavy use of strong acids and strong bases. Make sure to keep your area clean and put all equipment away after each lab. In addition, it is of the utmost importance that all digital analytical balances be kept SPOTLESS. Lab conduct will help to determine borderline grades.
Academic Dishonesty and Plagiarism: The following is taken from the Monmouth College policy on academic dishonesty:
We view academic dishonesty as a threat to the integrity and intellectual mission of our institution. Any breach of the academic honesty policy – either intentionally or unintentionally - will be taken seriously and may result not only in failure in the course, but in suspension or expulsion from the college. It is each student’s responsibility to read, understand and comply with the general academic honesty policy at Monmouth College, as defined here in the Scots Guide, and to the specific guidelines for each course, as elaborated on the professor’s syllabus.
The following areas are examples of violations of the academic honesty policy:
1. Cheating on tests, labs, etc;
2. Plagiarism, i.e., using the words, ideas, writing, or work of another without giving appropriate credit;
3. Improper collaboration between students, i.e., not doing one’s own work on outside assignments specified as group projects by the instructor;
4. Submitting work previously submitted in another course, without previous authorization by the instructor.
Please note that this list is not intended to be exhaustive.
Supplemental Instruction (SI):
A Supplemental Instruction (SI) component will be provided for all students in CHEM 220 this semester who want to improve their understanding of the material taught in this course. SI sessions will be led by a fellow student, Max Holle, who has already mastered the course material and has been trained to facilitate group sessions where students can meet to compare class notes, review and discuss important concepts, develop appropriate strategies for studying, and prepare for exams. Attendance is FREE and voluntary. Students may attend as many times as they choose. There will be three (3) available SI sessions offered per week.
Once they are determined, session days and times will be posted in the classroom and online at
You can contact the Teaching and Learning Center at (309) 457-2257 if you have questions about the SI session schedule.
SI leaders also have posted office hours and you are welcome to visit them during that time for additional assistance with class questions and material.
Tutoring:
The Teaching and Learning Center offers peer tutoring for CHEM 220 this semester. Ian Salveson will be your peer tutor.
Peer tutors are friendly and patient students who reinforce classroom learning, exam strategies, and study skills. Peer tutors are not there to give you the answers, but rather to challenge you how to learn the material. To get the most out of your tutoring session, please come prepared with your notes, book, and questions.
If those designated drop in hours do not work or you feel you need additional 1-1 tutoring, you can make an appointment on our website at:
Attendance is FREE and voluntary. This is a great opportunity for you to get extra support! You can contact the Teaching and Learning Center at (309) 457-2257 if you have questions about the tutoring schedule or appointments.
Academic Support: Teaching & Learning Center:
The Teaching and Learning Center offers various resources to assist Monmouth students with their academic success. All programs are FREE to Monmouth students and are here to help you excel academically. These services are not just for struggling students, but designed to assist all students to get better grades, learn stronger study skills, and be able to academically manage your time here.
Visit the center at the 2nd floor of Poling Hall from 8am-4:30pm or on line at
or by email at tlc@monmouthcollege.edu or by phone at 309-457-2257
Disability Support Services:
Monmouth College wants to help all students be as academically successful as possible. It is the goal of Monmouth College to accommodate students with disabilities pursuant to federal law, state law, and the college’s commitment to equal educational opportunity. Any student with a disability who needs an accommodation should speak with the Teaching and Learning Center. The Teaching and Learning Center is located on the 2nd floor of Poling Hall, 309-457-2257, or
Spring 2015 Lab Schedule
|Week |Date |Lecture |Chap(s) |Lab |Deadlines |
|1 |1/13 |Lab expectations | |Check-In |Results DUE |
| |(1/15) |Glassware |2.4 - 2.6 |Solution Chemistry Lab |immediately after lab |
| | |Pre-lab | |Lab #1 | |
|2 |1/20 |Sources of Error |3.3,3.5 |Limiting/Excess Reagent Lab |Results DUE |
| |(1/22) |Statistics |4.1,4.2, |Lab #2 |immediately after lab |
| | | |4.3,4.6 |Prep for Lab #5 | |
|3 |1/27 |Statistics |4.1,4.2, |Ksp – Part I | |
| |(1/29) |Beer’s Law Review |4.3,4.6 |Lab #3 | |
| | | |4.7,4.8 |Prep for Lab #5 | |
|4 |2/3 |Lab Quiz |7.1,7.2 |Equilibrium Constant Lab |Results Sheet DUE |
| |(2/5) |Titrations | |Lab #4 |2/10 (2/12) |
| | |Journal Article Summary | | | |
|5 |2/10 | JAS Ksp DUE | |Ksp – Part II |Results Sheet and Introduction DUE |
| |(2/12) |Writing Introductions | |Lab #3 continued |2/17 (2/19) |
|6 |2/17 |No Lecture | |No Lab | |
| |(2/19) |Lab #3 DUE | | | |
|7 |2/24 | | | |Results Sheet, Abstract and |
| |(2/26) |JAS Acid/Base DUE | |Acid/Base Titration |Introduction |
| | |Writing Abstracts | |Lab #5 |DUE 3/17 (3/19) |
|8 |3/3 |JAS Weak Acid DUE | |Weak Acid Titration |Results Sheet and |
| |(3/5) |Polyprotic Acids |10.1,10.3 |Lab #6 |Results/Discussion DUE 3/24 (3/26) |
|9 |3/10 |Spring Break | |Spring Break | |
| |(3/12) |No class | |No Lab | |
|10 |3/17 |Writing Results/Discussion | |Making Buffers |Results Sheet |
| |(3/19) |No JAS for Buffer Lab | |Lab #7 |DUE |
| | |Discuss Group Projects | |Discuss Group Projects |3/25 (3/27) |
|11 |3/24 |Lab Quiz | | | |
| |(3/26) | | |No Lab |Group Project Proposal Sheet Due |
| | |Chromatography |23.2,23.3 |Work on Preparing for your Group Projects |3/31(4/2) |
| | |Separations and GC |24 | | |
|12 |3/31 | | |Group Projects |Group PowerPoint Presentations and |
| |(4/2) |Question Hour | |*Proposals due at end of lab |Group Lab Report (full report) DUE|
| | | | | |on May 13 (3pm) |
|13 |4/7 |Lab Quiz | |Electrochemical Cells | |
| |(4/9) | | |Lab #8 |Results Sheet DUE |
| | |JAS EC DUE | | |after lab |
| | | | |Group Projects | |
|14 |4/14 |Question Hour | |Group Projects | |
| |(4/16) | | | | |
|15 |4/21 |Question Hour | |Group Projects | |
| |(4/23) | | | | |
| 16 |4/28 |Founder’s Day | |Group Projects for | |
| |(4/30) |No Lecture T or R | |Thursday Lab | |
| | |No Tuesday Lab | | | |
| 17 |5/5 |No Lecture T or R | |Group Projects for | |
| | |No Thursday Lab | |Tuesday Lab | |
Lab Notebook Guidelines
1. You must use a notebook that has copies (carbonless preferred) and write in pen. You can continue in your General Chemistry lab notebook if you have room.
2. A Table of Contents is needed at the beginning of your lab notebook and should include the following:
a. name of experiment
b. date of experiment
c. pages where experiment is located in your notebook
3. Pre-lab information
**Pre-lab info. will be checked by your lab TA before each lab or you will have a quiz on the pre-lab information which you will be allowed to use your notebook for. You will not be allowed to start the lab without the proper pre-lab information. Pre-lab is to your benefit especially when it comes to SAFETY!
a. Pre-lab information that your notebook must contain includes the following:
1. updated Table of Contents
2. lab title
3. date of experiment
4. lab objective
5. a list of chemicals to be used for that experiment
a. the properties of those chemicals (Merck Index or CRC)
b. safety hazards of those chemicals (MSDS or SDS; there are online versions)
6. a list of any balanced chemical reactions to be used for the experiment if necessary
7. calculations needed to start your lab (for example, those needed for preparing solutions)
4. Experimental Methods – The entire procedure need not be written; however, you cannot start lab without your lab manual *this section is checked after the lab is completed
IMPORTANT: Any variations from the experiment found in the lab manual should be included
a. Items to include in the experimental methods section include the following:
1. names of glassware/instruments used
2. how you prepared your samples and/or solutions
3. molarities of solutions used or made
4. how many samples you analyzed; how many trials you did
5. Observations and Results *this section is checked after the lab is completed
a. list any important observations you made during the experiment
b. list any problems that you encounter in the experiment
c. record the data that you obtain
d. perform all necessary calculations needed to get the final results *checked when results sheet is handed in
NEVER erase (which is why you are using a pen) data. Cross out, initial, and explain what occurred.
6. Initial and date the bottom of each page of your lab notebook.
7. Always record directly into your lab notebook. If your lab assistant or your instructor sees that you are not recording into your lab notebook (and instead onto another piece of paper or another notebook) you will receive a zero for your lab notebook that day.
WEEK #1 - LAB #1– Jan 13 or Jan 15
Solution Chemistry
OBJECTIVE: The primary objective of this lab is to practice and fine-tune your solution preparation skills.
INTRODUCTION/THEORY: In this lab, you will witness the chemistry behind dyeing fabric. There are three fabric dyes, red, blue, and yellow, which you will quantitatively measure and dissolve in water with salt and urea. Urea, H2NCONH2, is a water –soluble compound that, due to its hydrophillic properties, keeps the fabric moist during the dying process. Before the fabric is dyed, it is washed with a solution of soda ash (sodium carbonate). Due to the basicity of the soda ash solution, the OH bond on the cellulose (the chemical makeup of the fabric) loses a H+ resulting in an O- . The O- is now a binding site for the dye.1 The dye solutions of the primary colors will then be mixed to form other colors which will all be quantitatively deposited onto your fabric with a micropipette.
EXPERIMENTAL PROCEDURE #1:
You will work as a class in teams of 4 for this lab
The following steps need to be performed. It will be up to the group as to how to distribute the work.
1. Cover your lab bench space area with Saran Wrap and take a bandana and write your name on it in BIG letters in one of the corners with a black Sharpie.
2. Put your marked bandana in a beaker and fill it with enough pre-wash solution of soda ash (already made) so that your bandana is fully covered with solution. LIMIT contact of the soda ash solution with your skin as it is BASIC. There are gloves in the lab that you can wear.
3. Each team of 4 will make a solution of a different dye (red, blue, or yellow)
4. Weigh out the amount of dye needed to make 200 mL of dye solution (1fl.oz. = 29.57mL)
Red – 2.03g in 8oz of water
Blue – 4.29g in 8oz of water
Yellow - 2.47g in 8oz of water
** Show all calculations in your notebook for your pre-lab
5. Weigh out the amount of salt (NaCl) needed so that the concentration of salt (NaCl) in your dye solution is 2.14M.
** Show all calculations in your notebook for your pre-lab
6. Weigh out the amount of urea needed so that the concentration of urea in your dye solution is 0.29M.
** Show all calculations in your notebook for your pre-lab
7. Measure out 200mL of water (decide what you will use to measure out the water) and mix the dye with the salt and urea. Once your dye solution is made, place it at the front of the lab for others to use.
8. Remove your bandana from pre-wash solution, ring dry (the drier; the better) and lay flat (try to remove wrinkles) on your lab bench on top of some Saran Wrap.
9. Each group member should now measure out 5mL of each dye (red, blue, and yellow) with a graduated cylinder and pour into small beakers.
10.With a micropipette, each person should accurately pipet 100µL of each dye into their well-plate according to the matrix below. For example, 100µL of red should be added to 100µL of red. Fill in the colors that you make!
If available, use the pipets that are marked 10-100. The pipets marked 100-1000 or P1000 can be used but are not as accurate.
| |R |Y |B |
|R | | | |
|Y | | | |
|B | | | |
11. From the additional colors made in step 10 and the original colors, each person should now again accurately pipet 100µL of each dye into their well-plate according to the matrix below. For example, 100µL of red should be added to 100µL of orange (that you made in step 10).
If available, use the pipets that are marked 10-100. The pipets marked 100-1000 or P1000 can be used but are not as accurate.
| |O |P |G |
|R | | | |
|Y | | | |
|B | | | |
12. Modeling the 12 color wheel below, add your colors to your bandana in 10µL amounts with a micropipette. Be accurate in the placement of your colors.
If available, use the pipets that are marked P10, P20, or 2-20.
EXPERIMENTAL PROCEDURE #2:
You will work as a class in teams of 4 for this lab
The following steps need to be performed. It will be up to the group as to how to distribute the work.
1. Make a 30 color wheel around your original 12 color wheel modeling the figure below. You should have enough of your original red, yellow, and blue dye to do this.
a. Use the multiwells to make the mixtures such as the R:Y 90:10.
b. Add the color mixtures to your bandana in 10µL amounts with a micropipette. Be accurate in the placement of your colors.
If available, use the pipets that are marked P10, P20, or 2-20.
2. When you are finished, let your bandana to dry on your benchtop along, leave the Solution Chemistry Lab Grade Sheet (next page of your notebook) which should have your name on it, and leave your lab notebook copies. Also, make sure your area is clean.
Solution Chemistry Lab
Grade Sheet
|Name | |
|Maximum grade that can be earned |100 |
| | |
|Pipet Spot Size / Application (-10 maximum for incorrect volumes and | |
|poor application of solution) | |
|Color Matching (-5 maximum for not matching colors in wheel) | |
|Mixing in Wells (-1 for each solution not mixed) | |
|Circle (-1 if not a circle) | |
| | |
|Grade | |
WEEK #2 - LAB #2 – Jan 20 or Jan 22
Visualizing a Limiting/Excess Reagent Reaction
OBJECTIVE: The primary objective of this lab is to qualitatively visualize limiting and excess reagents through careful quantitative measurements of the reagents.
THEORY: In this lab, known amounts of NaHCO3 (baking soda) and vinegar (5% acetic acid) will be mixed to form CO2 and other products. You are responsible for determining the other products that form. The amount of CO2 that is formed will be visualized through the use of balloons and will depend on the limiting reagent.
CHEMICAL REACTION:*put in your lab notebook for your pre-lab
[pic]
EXPERIMENTAL PROCEDURE #1:
**Before starting, measure out enough water to boil so that you have 1000 mL of cooled, boiled water. This is for Prep for Lab #5 (page 17) which you need to complete before leaving lab for the day. There is also a pre-lab calculation for this lab
You will work in teams of 6 for this lab
The following steps need to be performed. It will be up to the group as to how to distribute the work.
1. Weigh the following six amounts of baking soda (NaHCO3):
0.18 grams
0.35 grams
0.52 grams
0.70 grams
1.00 grams
1.70 grams.
2. Label the balloons 1-6.
3. Put the six different masses of baking soda into six different balloons using a small plastic funnel. Make sure the baking soda goes to the bottom of the balloon.
4. Transfer 10 mL of vinegar (5% acetic acid, HC2H3O2) into 6 different test tubes so 60 mL total
5. Attach the filled balloons to the mouth of the test tubes. Make sure that the contents of the balloon and test tube are not mixed.
6. After the balloons are securely attached to the test tubes, each group member needs to lift a balloon on one of the test tubes so that the contents of the balloon mix with the test tube contents. Make sure the balloons are held on tightly to the test tube. All six test tubes should be reacted simultaneously. When the reactions are done, record your observations in the table on the next page. **You will rip this table out and leave on the benchtop when you are finished with the lab.
| | | | | | |
|Test Tube |Mass |Moles |Volume |Moles |Chem rxn mole ratio |
| |NaHCO3 |NaHCO3 |vinegar |acetic |NaHCO3: |
| |weighed out |weighed out |mL |acid |acetic acid |
| | | |measured | | |
|1 |1.00 |5.00 |4.00 | | |
|2 |2.00 |5.00 |3.00 | | |
|3 |3.00 |5.00 |2.00 | | |
|4 |4.00 |5.00 |1.00 | | |
Part 2 - Determination of the Equilibrium Constant
1. Set up 10 clean test tubes in a rack and number them 1–10.
2. Obtain 20.00 mL of the stock solution of 0.00250 M Fe(NO3)3 in a small beaker.
3. Use the 0.100 M HNO3 that you prepared in Part 1.
4. Dispense the volumes of the stock solution of 0.00250 M KSCN that you will need into each test tube. (see table below)
5. Add the solutions of Fe+3 and HNO3 in the proportions listed below to the SCN- already in your test tubes. Use glass stirring rods to insure that the solutions are well mixed. Use a different pipet for each solution, and label them so that you don't get them mixed up.
6. Measure and record the absorbance of each solution at 450 nm.
7. Leave all copies from your lab notebook at your lab station.
|Test Tube # |0.00250 M Fe(NO3)3 |0.00250 M KSCN |0.100 M HNO3 |Absorbance at 450 nm|[FeSCN2+]eq |
| |(mL) |(mL) |(mL) | |to be determined |
| | | |DILUTE | |later |
| | | |Acid | |from plot |
|1 |1.00 |1.00 |5.00 | | |
|2 |1.00 |1.50 |4.50 | | |
|3 |1.00 |2.00 |4.00 | | |
|4 |1.00 |2.50 |3.50 | | |
|5 |1.00 |3.00 |3.00 | | |
|6 |2.00 |1.00 |4.00 | | |
|7 |2.00 |1.50 |3.50 | | |
|8 |2.00 |2.00 |3.00 | | |
|9 |2.00 |2.50 |2.50 | | |
|10 |2.00 |3.00 |2.00 | | |
Post-Lab CALCULATIONS: Put all Calculations in your Lab Notebook and hand in on due date listed in your lab schedule
1. For Part I, calculate the [FeSCN+2] of your 4 standard solutions based on the limiting reagent in the reaction and accounting for dilution. Put this concentration in your table.
2. For data in Part 1, plot absorbance (y axis) vs [FeSCN+2] that you calculated in #1 (x axis) , and confirm that the points fall along a straight line. This is your Beer’s Law Plot. (Do not set the intercept to zero.) Attach your Beer’s Law Plot to your results sheet (next page)
3. For Part II, calculate the equilibrium [FeSCN+2] for each test tube 1–10 using the measured absorbance and the equation from the Beer’s Law plot and put in the table. This reaction is not a limiting/excess reagent reaction since it is in equilibrium. Put these values in the third column of the results sheet (next page)
4. For Part II, compute the initial moles of Fe+3 and moles of SCN– in each of the ten test tubes based on the volumes that you measured out for each reaction.
5. For Part II, use your equilibrium [FeSCN+2] that you determined in #3 and the total volume to calculate the eq moles of FeSCN+2 that formed.
6. For Part II, using the moles in #4 and #5, calculate the equilibrium [Fe+3] and [SCN– ] for the ten trials. Again, keep in mind that after reaction, you have a total volume. Put these values in the first two columns of the results sheet (next page)
7. For Part II, once the equilibrium concentrations of all species have been determined, calculate the equilibrium constant for each trial. Then compute the average Keq and standard deviation among the ten test tubes. Put these values in the fourth column of the results sheet (next page)
8. Calculate the mean and standard deviation for your Keq and put this on the results sheet (next page) Hand in your results sheet, calculations, and Beer’s Law Plot on the date due that is listed on your lab schedule.
Results Sheet – Lab #4 – Equilibrium Constant
NAME __________________________________________________
DATE__________________________
[Fe+2]eq [SCN-1]eq [FeSCN+2]eq Keq
1. ______________1.____________ 1. ____________________________ 1.
2. ______________2.___________ 2. ____________________________ 2.
3. ______________3.__________ 3. ____________________________ 3.
4. ______________4.__________ 4. ____________________________ 4.
5. ______________ 5.__________ 5. ____________________________ 5.
6. ______________6. __________ 6. ____________________________ 6.
7. ______________7.____________ 7. ____________________________ 7.
8. ______________8.___________ 8 ____________________________ 8.
9. _______________9.___________ 9. ____________________________ 9.
10. _____________10.___________ 10. ____________________________ 10.
Mean_________________________
Standard Deviation
**Attach Beer’s Law Plot, your grade sheet (next page) for this lab, and your calculations.
Equilibrium Constant
Grade Sheet
| [Fe+2]eq (5/5) | |
| [SCN-1]eq (6/6) | |
| [FeSCN+2]eq (6/6) | |
| Keq (4/4) | |
| | |
|Standard Deviation (2/2) | |
|Mean (2/2) | |
| | |
|Beer’s Law Plot (5/5) | |
| | |
|Accuracy (5/5) | |
|Precision (5/5) | |
| | |
|Total (40/40) | |
WEEK #5 - LAB #3 – Feb 10 or Feb 12
What is the Solubility Product Constant of a Slightly Soluble Salt?
OBJECTIVE: In this lab experiment, you will determine the solubility product constant of a slightly soluble salt.
THEORY: In order to determine the maximum solubility of a salt, you need to have the salt in the presence of excess solid. The magnitude of the solubility product constant (Ksp) gives you an idea of the maximum solubility of the salt. Most values of Ksp are small such as the Ksp for AgCl which is equal to 4 x 10-11. In this lab, you will determine the Ksp for calcium iodate, Ca(IO3)2 through a starch titration with sodium thiosulfate that will determine the concentration of the iodate ion. The reaction that describes the equilibrium of Ca(IO3)2 with its ions is as follows
Ca(IO3)2 (s) [pic] Ca+2 (aq) + 2 IO3– (aq)
and the solubility product expression is
Ksp = [Ca+2] [IO3–]2
The ionic equations for the titration reactions are:
IO3- + 5I- +6H+ 3I2 + 3H2O
I2 + 2S2O32- 2I- + S4O62-
deep blue colorless
with starch
In the presence of starch, the I2 forms a dark blue complex. To determine the concentration of iodate in the unknown solution you will add the starch indicator and then titrate with Na2S2O3 until the dark blue color disappears.
EXPERIMENTAL PROCEDURE – Week 1 Already completed (page 18)
EXPERIMENTAL PROCEDURE – Week 2
Standardization of Thiosulfate Solution (titrant) to determine it’s concentration to 4 sig figs
1. Set up a buret and fill it with the 0.1M thiosulfate (Na2S2O3) solution (made week 3 (page 18)).
2. Pipet four 25.00 mL aliquots of the 1.500 x 10-2 M KIO3 solution (week 3) into four 250 mL Erlenmeyer flasks.
*** Completely finish one trial before beginning the next (store the samples which are not being used in the dark). Read all of the next paragraph before beginning your titrations.***
3. Add 2 grams NaI (iodate free).
4. When solution is complete, add 10 mL 1.0 M HCl. *Pre-lab Calculation – making 1.0M HCl from concentrated HCl
5. TITRATE IMMEDIATELY with the thiosulfate solution until the color becomes pale yellow.
6. Add 5 mL of the starch solution and titrate to the disappearance of the starch-blue/black color.
HINT: the dark blue/black solution will start to become slightly transparent as you near the endpoint. The solution should remain COLORLESS for 15 seconds.
7. Once again, add the thiosulfate solution slowly near the equivalence point. You should be able to measure this end point to within 1/2 drop of the true equivalence point.
8. Repeat the titration two more times.
Determination of [IO3–]eq in the Saturated Solution of Ca(IO3)2
1. Pipet 10.00 mL of the filtrate from part 1 of this lab made in week #3 into a clean Erlenmeyer flask.
2. Add about 20 mL of deionized water to the flask.
3. Dissolve about 2 g of solid KI in the solution. Add 20 drops of 2 M HCl and mix thoroughly. The solution should take on a brown color. . *Pre-lab Calculation – making 2M HCl from concentrated HCl
4. Titrate the mixture with YOUR standardized Na2S2O3 (the 0.1M solution that you now know to 4 sig figs if you do the calculations) until the brown color changes to yellow.
5. Add several drops of starch to the solution, enough to turn the solution blue/black.
6. Continue titrating with YOUR standardized Na2S2O3 until the blue/black color just disappears.
7. Repeat the titration two more times.
****Leave your lab notebook copies at your lab station.
Post-Lab CALCULATIONS to be handed in with your results sheet and Introduction on the date specified on your lab schedule:
1. Using the information from your first set of titrations, calculate the concentration of the standardized sodium thiosulfate solution along with the average and standard deviation and put in the first column of the results sheet (next page).
2. Using the calculated concentration of your standardized sodium thiosulfate from #1 along with your information from the second set of titrations, calculate the [IO3–]eq in the filtrate for each trial. Put these numbers in column two of the results sheet (next page).
3. From the [IO3–]eq for each trial calculated in #2, calculate the solubility of [Ca+2]eq for each trial and put these numbers in column three of the results sheet (next page).
4. Using your equilibrium concentrations, calculate the Ksp values for each trial along with the average Ksp of Ca(IO3)2 and the standard deviation. Put these numbers in column four of the results sheet (next page). Hand in your results sheet, calculations, and with your introduction on the date specified in your lab manual.
Results Sheet - Determining Ksp
NAME __________________________________________________
DATE __________________________
[ Na2S2O3] - titrant [IO3-1] [Ca+2] solubility Ksp
1. __________________________ 1. _______________1._____________ 1.
2. __________________________ 2. ________________2.____________ 2.
3. __________________________ 3. ________________3.___________ 3.
Average_________________________ Average
Standard Dev Standard Dev
*Attach your calculations, introduction, and grade sheet (next page) for this lab
Determining Ksp
Grade Sheet
|Molarity of Titrant (9/9) | |
|Equilibrium M of Iodate (6/6) | |
|Equilibrium M of Calcium (3/3) | |
|Ksp (9/9) | |
| | |
|Standard Deviation (4/4) | |
|Mean (4/4) | |
| | |
|Accuracy (5/5) | |
|Precision (5/5) | |
| | |
|Introduction (10/10) | |
| | |
|Total (55/55) | |
WEEK #6 – NO LAB
Feb 17 or Feb 19
WEEK #7 - LAB #5 – Feb 24 or Feb 26
How much ACID is in your unknown sample? An Acid/ Base Titration
OBJECTIVE: The primary objective of this lab is to determine to 4 significant figures the % of acid in your unknown sample by the analytical technique known as acid/base titration. In order to achieve ultimate accuracy, you will need to standardize your titrant, NaOH, to 4 significant figures.
THEORY: In this lab, a sample of an unknown amount of acid, potassium hydrogen phthalate (KHP), will be titrated with a base, sodium hydroxide (NaOH), to determine the amount of acid in the sample. The base is referred to as the titrant. Since 1 mole of acid (KHP) reacts with 1 mole of base (NaOH), the volume and molarity of the base (titrant) can be used to determine the moles of acid in your unknown sample. Due to the use of an indicator, phenopthalein, the sample of unknown acid will turn slight pink when the number of moles of base equals the number of moles of acid. To determine the % of acid in your sample accurately, the molarity of the base (titrant) needs to be known to 4 significant figures (standardizing your titrant). This is possible by titrating a known amount of KHP with the NaOH that you make. Once again, if you know the moles of the acid and the volume of the base (titrant) used to turn the acid solution pink, then you can determine the molarity of the base (titrant). The following equations will be helpful:
KHP + NaOH NaKP + H2O
HP- + OH- P2- + H2O
EXPERIMENTAL PROCEDURE:
Standardization of Titrant (Base – NaOH)
1. Titrate known KHP samples (out in week #3) with 0.1XXXM NaOH solution(week 2)
a. Take your three 0.75 gram samples (+/−0.1 mg) of KNOWN KHP that you already weighed out and dissolve each in 50mL of distilled water. Pre-lab Question – How will you measure out the volume of water?
b. Add two drops of phenolphthalein indicator. Always swirl your sample as you titrate.
c. Rinse your buret with your 0.1XXXM sodium hydroxide solution (that you made in week #2) and then fill your entire buret with this solution.
d. Titrate with your 0.1XXX M sodium hydroxide until a FAINT PINK COLOR persists for 30
seconds (exposure to air causes this end-point to gradually fade back to a colorless
solution). Fractional drops should be added as the end-point is being approached. Try
to obtain in the same FAINT PINK COLOR in all the trials (this is difficult because the
endpoint fades, making direct comparison unreliable).
e. Calculate how much NaOH in mL was needed to titrate your first known KHP sample. Use this information of the number of mL of NaOH needed per gram of known KHP to estimate the number of mL of NaOH needed for the other titrations of your known KHP.
f. CONTINUE AS SOON AS POSSIBLE WITH THE UNKNOWNS!! NaOH is unstable when exposed to the air. KEEP TIGHTLY CAPPED! It is possible to do all the titrations of this lab in one day.
Determine % acid (KHP) in Unknown Sample
1. Weigh Out Unknown KHP Sample (by difference) – Need to get this from your TA
a. Perform a preliminary titration on the unknown.
1. Weigh out approximately one gram of the unknown KHP into a 250 mL flask
2. Add 50 mL of water and two drops of phenolphthalein.
3. Titrate to a faint pink color using your standardized 0.1XXX M NaOH.
a. Use this trial to adjust your sample size so the titration will require < 50 mL of
the standardized 0.1XXX M NaOH (the maximum sample size should not
exceed 2 grams).
4. Using the adjusted sample size, weigh out three samples (+/− 0.1 mg) of the
UNKNOWN KHP into 250 mL Erlenmeyer flasks (make sure the flasks are labeled).
Weigh out your samples by difference from a weighing bottle.
2. Titrate the Unknown KHP Samples
a. Titrate these samples using the same procedure that was used for the knowns.
b. When you are finished, drain the NaOH out of your buret and rinse it with water
(including the tip).
c. Always store your buret with water in it..
*BEFORE leaving lab, put your lab notebook copies at your lab station
SAVE YOUR NaOH !!
Post –Lab CALCULATIONS to be handed in with your results sheet, abstract, and introduction on date listed in your lab schedule.
1. Using the information from the first set of titrations (standardization of titrant), calculate the average molarity of your NaOH from the individual molarities determined for each trial. Also calculate the Standard Deviation (SD). Put this data on your results sheet (next page).
2. Using the now standardized molarity of the NaOH calculated in #1, determine the grams of KHP in your unknown for each trial.
3. Using the data calculated in #2, determine the % KHP in your unknown for each trial along with the SD. Put this data on your results sheet (next page).
4. Turn in your results sheet, calculations, abstract, and introduction on the date listed on your lab schedule.
Results Sheet–Acid/Base Titration (KHP)
NAME __________________________________________________
DATE __________________________
Concentration of Titrant NaOH (MOLARITY) UNKNOWN ACID (KHP) PERCENTAGE (%)
1. __________________________ 1. ____________________________
2. __________________________ 2. ____________________________
3. __________________________ 3. ____________________________
================================== ====================================
Average ______________________ Average _________________________
Standard Dev Standard Dev
*Attach your calculations, abstract, introduction, and your grade sheet for this lab (next page)
Acid/Base Titration - KHP
Grade Sheet
|Molarity of Titrant (9/9) | |
|Percent KHP (12/12) | |
|Average (3/3) | |
|Standard Deviation (3/3) | |
| | |
|Accuracy (5/5) | |
|Precision (5/5) | |
| | |
|Abstract (10/10) | |
|Introduction (13/13) | |
| | |
|Total (60/60) | |
WEEK #8 - LAB #6 – March 3 or March 5
Weak Acid Titration - Analysis of Citric Acid in 7-Up
OBJECTIVE: The primary objective of this lab is to determine the 3 Ka values and the concentration of citric acid in 7-Up through the use of a pH meter to generate a titration curve.
INTRODUCTION: In this lab, known volumes of de-gassed 7-Up will be titrated with your standardized NaOH from Lab #5. Through a series of calculations and your knowledge of titrations, you will statistically determine the Ka values for citric acid and the concentration of citric acid in your 7-Up.
CHEMICAL REACTIONS: *need for pre-lab
EXPERIMENTAL PROCEDURE: *you will work with a partner for this lab
1. Obtain a pH meter and calibrate it with the following buffers: (Instructions to calibrate will be on the white board in the lab)
pH 4 – red ; pH 7 – yellow; pH 10 - blue
2. Take some time to set-up your buret, pH meter, Erlenmeyer flask, and stir plate. You will need the pH meter to be immersed but not to touch the stir bar.
3. Obtain 50.00 mL of degassed 7-Up and dispense into your 250 mL Erlenmeyer flask.
4. Add 2- 3 drops of phenopthalein to your flask.
5. Rinse your buret with you or your partner’s standardized NaOH solution from lab #5 (use average M to 4 sig figs that you calculated in your previous lab when doing calculations) and then fill your entire buret with this solution.
6. ROUGH TITRATION - Titrate with your standardized NaOH until a FAINT PINK COLOR persists for 30 seconds (exposure to air causes this end-point to gradually fade back to a colorless solution). Fractional drops should be added as the end-point is being approached. Record the pH throughout.
7. ACCURATE TITRATIONS – Do three more titrations adding the smallest amounts in mL of your NaOH so that you have enough points around the endpoints to calculate the Ka values for citric acid and the molarity of citric acid in 7-Up. Record the pH throughout. Make sure that your pH levels off before stopping your titration so that you get a complete titration curve.
****Leave your lab notebook copies at your lab station.
Post-Lab CALCULATIONS: *Due along with results sheet and results/discussion on date listed in lab schedule
1. Plot the following curves for all three accurate trials
(1) pH (y axis) vs volume NaOH (mL) added (x axis) to form a titration curve
(2) change in pH / change in NaOH (mL) on the y axis vs volume NaOH (mL) added on the x axis to form the derivative of titration curve
(3) plot curves (1) and (2) on one graph – only need to turn in this one
2. Calculate the molarity of citric acid in your 7-Up for all three accurate trials. Calculate the average molarity and the standard deviation. Put all data on results sheet (next page) **HINT – think about the KHP lab but remember that you are dealing with a triprotic acid!!!
3. Calculate the grams of citric acid in 1 can of 7-Up that you determined from all three accurate trials. Calculate the average grams and the standard deviation. Put all data on results sheet (next page)
4. Using your graphs from #1 and your actual data, calculate pKa1, pKa2, pKa3 for the citric acid in your 7-Up for all three accurate trials. Calculate the average for all pKa values and the standard deviation for all. **HINT – For a monoprotic acid, pKa = pH halfway to equivalence. A triprotic acid has 3 equivalence points even if you cannot visualize them on your titration curve. Put all data on results sheet (next page).
Results Sheet–Weak Acid Titration
NAME __________________________________________________
DATE __________________________
Concentration of Citric Acid (MOLARITY) Grams of Citric Acid in 1 can of 7-Up
Trial 1. __________________________ Trial 1. ____________________________
Trial 2. __________________________ Trial 2. ____________________________
Trial 3. __________________________ Trial 3. ____________________________
================================== ====================================
Average ______________________ Average _________________________
Standard Dev Standard Dev
pka1 values pka2 values
Trial 1. __________________________ Trial 1. ____________________________
Trial 2. __________________________ Trial 2. ____________________________
Trial 3. __________________________ Trial 3. ____________________________
================================== ====================================
Average ______________________ Average _________________________
Standard Dev Standard Dev
pka3 values
Trial 1. __________________________ *Attach your calculations, your graphs, and grade sheet
Trial 2. __________________________ *Attach your results/discussion
Trial 3. __________________________
==================================
Average ______________________
Standard Dev
Weak Acid Titration- Grade Sheet
|Concentration of Citric acid (9/9) | |
|Grams of Citric acid (9/9) | |
|pKa1 values (4/4) | |
|pKa2 values (4/4) | |
|pKa3 values (4/4) | |
| | |
|Average (5/5) | |
|Standard Deviation (5/5) | |
| | |
|Accuracy (10/10) | |
|Precision (5/5) | |
| | |
|Results (20/20) | |
|Discussion (25/25) | |
| | |
|Total (100/100) | |
Results (20/20)
Titration Curves – 3 of them
Curve correctly plotted (3/3)
Axis labeled (3/3)
Figure Caption (3/3)
Derivative Curves – 3 of them
Curve correctly plotted (3/3)
Axis labeled (3/3)
Display the pka values that you found (3/3)
Display the Concentration and/or the grams of Citric acid that you found (2/2)
Discussion (25/25)
Passive Voice (2/2)
Explain data (10/10)
Discuss accuracy of your data (5/5)
Discuss precision of your data (5/5)
Discussion flowed well (3/3)
WEEK #9 – NO LAB
Spring Break!
March 10 or March 12
WEEK #10 - Lab #7- March 17 or March 19
Buffers: Preparation and Analysis
Summary:
This lab involves the preparation and analysis of an acetic acid/acetate buffer. You will make this buffer by two methods, compare its ability to resist change in pH with that of a solution of just acetic acid and just the acetate anion, and ultimately determine the buffer capacity. A pH meter will be used in order to determine the pH accurately.
Reactions: *Pre-lab
1. Write the acid dissociation reaction for acetic acid
2. Write the base dissociation reaction for the acetate anion
3. Write the reaction involving the addition of strong base to a solution of acetic acid
4. Write the reaction involving the addition of strong acid to a solution of acetate anion (source is sodium acetate)
What is a buffer?
Buffers are a solution of a weak acid and a conjugate base or a weak base and a conjugate acid that resist changes in pH when a strong acid or a strong base is added.
How do buffers resist change in pH?
As you already know from working with titration problems, when you add a small amount of strong base (OH-) to a system that already contains both the weak acid (HA) and the conjugate base (A-) , the strong base reacts with the weak acid to produce conjugate base. The conjugate base is a weak base and therefore only produces a small amount of OH- in solution upon dissociation.
HA + OH- A- + H2O
A- + H2O [pic] HA + OH-
*Pre-lab question
Write the reactions for the scenario of the addition of strong acid to a system of a weak base and conjugate acid.
What is the “buffering range”?
The “buffering range” of a buffer is +/- 1 pH unit of its pKa.
What is the “buffer capacity”?
The “buffer capacity” is the measure of resistance that a buffer has to pH change.
Part I:
*Pre-lab Calculation A
1. Determine the pH of a 0.10 M sodium acetate solution.
2. Determine the amount of 1.0 M HCl needed to add to achieve a pOH equal to the pkb of the acetate anion if you have 25 ml of the 0.10M sodium acetate solution to start.
Experiment A
1. Make a 25 mL solution of 0.10 M sodium acetate in water.
2. Measure the pH of the solution.
3. Add dropwise (with your buret) 1.0 M HCl.
4. Record the pH of the solution every few drops until the pH equals the pKa of the acetic acid. *Note mL
5. Add dropwise (with your buret) 1.0 M NaOH *Note pH and mL along the way
6. Record the volume of NaOH that can be added until the pH changes by more than 0.2 pH units.
7. Record your observations
*Pre-lab Calculation B
1. Determine the pH of a 0.10 M acetic acid solution.
2. Determine the amount of 1.0 M NaOH needed to add to achieve a pH equal to the pka of acetic acid if you have 25 ml of the 0.10M acetic acid solution to start.
Experiment B
1. Make a 25 mL solution of 0.10 M acetic acid in water.
2. Measure the pH of the solution.
3. Add drop wise (with your buret) 1.0 M NaOH
4. Record the pH of the solution every few drops until the pH equals the pKa of the acetic acid. *Note mL
5. Add drop wise (with your buret) 1.0 M HCl *Note pH and mL along the way
6. Record the volume of HCl that can be added until the pH changes by more than 0.2 pH units.
7. Record your observations.
Part II on NEXT PAGE
Part II:
*Pre-lab Calculation A
1. Determine the number of grams of sodium acetate and the amount of mLs of 6.00 M acetic acid that you would need to make 50.00 mL of a sodium acetate/acetic acid buffer solution at the pH equal to 5.00 in order to make a buffer with a final concentration of 0.05M.
*Pre-lab Calculation B
2. Determine the number of grams of sodium acetate and the amount of mLs of 6.00 M acetic acid that you would need to make 50.00 mL of a sodium acetate/acetic acid buffer solution at the pH equal to 5.00 in order to make a buffer with a final concentration of 0.10M.
Experiment A and B
1. Make a sodium acetate/acetic acid buffer with the amounts of each that you predetermined in Part II A
2. Record the pH.
3. Adjust the pH to equal the pKa by adding some concentrated HCl or NaOH.
4. Record the amount and solution added.
5. Demonstrate to your TA or instructor that the pH will not change if more concentrated HCl or NaOH is added. *Note the concentration that you are using.
6. Determine the volume of HCl or NaOH that can be added until the pH changes by more than 0.2 pH units.
7. Record your observations
8. Redo Steps 1-6 for part II B
****Leave your lab notebook copies at your lab station.
Results Sheet–Buffer Lab
NAME __________________________________________________
DATE _________________________
Buffer Capacity
Part I Experiment A__________________________
Part I Experiment B __________________________
Part II Experiment A __________________________
Part II Experiment B__________________________
**Attach a detailed response of your observations of systems of buffers along with your calculations
Throughout your buffer lab, you are asked to record observations. Please use all of these observations to write this response.
Buffer Lab
Grade Sheet
|Buffer Capacity Part I A (5/5) | |
|Buffer Capacity Part I B (5/5) | |
|Buffer Capacity Part II A (5/5) | |
|Buffer Capacity Part II B (5/5) | |
| | |
|Response (10/10) | |
| | |
|Total (30/30) | |
WEEK #11 – NO LAB
Work on Group Projects
March 24 or March 26
WEEK #12 – March 31 or April 2-
Project Proposal DUE
Project Title
Group Members
1.
2.
3.
4.
5.
What is the problem being addressed? (What is the goal of the research being proposed? What is the hypothesis being tested?
Why is the problem important and interesting?
What will you DO to address the problem? What is your experimental plan?
What resources (equipment, chemicals ...) do you need complete the research?
References (need at least 5)
PRE-LAB
WEEK #13 - LAB #8 – April 7 or April 9
Building Electrochemical Cells
Determining the Potential of Electrochemical Cells
1. List the Standard Reduction Potentials (E0) for the following half-cells.
a. Cu2+/Cu
b. Pb2+/Pb
c. Zn2+/Zn
2. Write the half reactions (oxidation and reduction) and the net cell reaction for the following electrochemical cells.
a. Cu2+/Cu and Zn2+/Zn
b. Cu2+/Cu and Pb2+/Pb
c. Zn2+/Zn and Pb2+/Pb
3. Calculate the theoretical cell potential for the following cells using Standard Reduction Potentials (assuming a concentration of 1M).
a. Cu2+/Cu and Zn2+/Zn
b. Cu2+/Cu and Pb2+/Pb
c. Zn2+/Zn and Pb2+/Pb
4. Write the Nearnst equation for the following half cells.
a. Cu2+/Cu
b. Pb2+/Pb
c. Zn2+/Zn
WEEK #13 - LAB #8 – Building Electrochemical Cells
Determining the Potential of Electrochemical Cells
OBJECTIVE: In this lab experiment, you will build several electrochemical cells and then determine the potential. In an electrochemical cell, chemical energy is converted into electrical energy. This is accomplished by using a spontaneous chemical reaction to generate an electric current, which we can simply define here as electrons traveling through a wire.
THEORY: To create the electrochemical cell, two half-reactions will be set up in different containers. In one, an oxidation reaction will be used to generate a source of electrons which will then travel, through an external circuit, to a second container where reduction takes place. A salt bridge will connect the two half cells to allow ions to flow for preventing charge buildup.
EXPERIMENTAL PROCEDURE – you will work in groups for this lab
1. Make sure that you know how to use the DC voltmeter that is at your lab station.
2. General Information for each electrochemical cell that you will make is below.
a. Create each half-cell by placing a metal electrode in an electrolytic solution
containing the same metal’s ions. For example the copper electrode will be placed
in a copper(II) nitrate solution (already made for you).
b. Each electrochemical cell you create you will require two half-cells. Set these cells
(beakers) beside each other – they will be connected by a U-tube (glass tube which
you will fill with KNO3).
c. Fill each beaker about two-thirds full of the electrolytic solution. Clean the electrode
using the steel wool, then place the electrode in its appropriate solution.
d. Clip one end of each copper wire to the two electrodes using the alligator clips.
e. Fill the U-tube with KNO3 and stopper both ends with the cotton plugs. Turn the U-
tube upside down and place one end in each half-cell.
f. Touch the other end of the copper wires to the voltmeter terminals. If the indicator on the voltmeter deflects in the wrong direction, switch the wires on the terminals. Read the highest voltage reading obtained – you’ll need to do this quickly after connecting the wires to the voltmeter.
DATA AND CALCULATIONS *Turn this in at the end of lab with your lab notebook copies and your grade sheet (next page)
1. All of the solutions are nitrate solutions of the cation. For example, for Cu2+, you have a Cu(NO3)2 solution.
2. Determine the cell potential (Voltage) of the following combinations of half-cells using your electrochemical setup (directions above) and your voltmeter.
|Half-cells |Cell Voltage |
|Cu2+|Cu |Zn2+|Zn | |
|Cu2+|Cu |Pb2+|Pb | |
|Zn2+|Zn |Pb2+|Pb | |
3. Compare the cell potentials you determined today with the theoretical potentials that you pre-determined from the Standard Reduction Potential.
4. From your date above, using the Nearnst equation, deduce the concentration of Cu2+ in the electrolyte solution that was made for you.
5. When you are finished, work on your group projects!
|Data (10/10) | |
| Voltages | |
| Concentration | |
| | |
| | |
| | |
| | |
| | |
| | |
|Total Points/Grade (10pts total) | |
Electrochemical Cells
Grade Sheet
WEEKS #14-17 – Work on Group Projects
At the end of your group project, you will be required to write a full lab report which should include the following:
Abstract
Introduction
Materials/Methods
Results/Discussion
References
You will also be required to present your project in the form of a PowerPoint on the day that is specified in your lab schedule. All group members must contribute equally to both the paper and the presentation.
On the next pages are evaluations that you will fill out for your group members at the end of the project.
CHEM 220 Lab Group Member Evaluations
Evaluator:
Group Members:
Topic:
How well did your group work together?
Please list the strengths and weaknesses of each one of your group members:
Additional Comments:
-----------------------
R
G
OY
BP
O
P
Y
B
RO
RP
BG
YG
R
G
OY
BP
O
P
Y
B
RO
RP
BG
YG
Y 100%
R:Y 10:90 100%
R:Y 50:50 100%
R:Y 40:60 100%
R:Y 30:70 100%
R:Y 20:80 100%
R:Y 60:40 100%
R:Y 70:30 100%
R:Y 80:20 100%
R:Y 90:10 100%
R100% 100%
B 100%
Reference
1. Bonneau, M.C., The Chemistry of Fabric Reactive Dyes, J. Chem. Ed., 1995, 72, (8), 724.
Ka1 Rxn
Ka2 Rxn
Ka3 Rxn
Net Reaction
[pic]
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