Inorganic Contaminants Present in Water Samples Presentation

PROJECT 1: INORGANIC CONTAMINANTS PRESENT IN WATER SAMPLES

1. INTRODUCTION

Although the use of performance enhancement drugs (PEDs) in sports (“doping”) was not historically regulated, nowadays PEDS are strictly regulated in all major sports, professional and amateur. Random, unannounced sampling (“screening”) controls are used to detect infractions to these rules. But, how can screeners collect a urine sample and tell if a drug was used? What kind of tests support the serious sanctions athletes face? This is just one illustration where the determination of a chemical substance and its amount is necessary. You or someone you know may have used chemical detection to tell if a substance is present in a sample. word image 2258

We can establish the identity of a chemical through properties unique to that chemical in addition to determining its potential uses. Chemical properties are studied by reacting materials with other chemicals; in other words, by observing their reactivity. Chemical reactivity is used to establish the identity of an unknown substance, an analyte. For example, unknown materials found in the environment (e.g. water, soil, air) or in other types of matrices (e.g. biological fluids, food products) can be identified by running a series of chemical tests (reactions) and comparing if the reactivity of the unknown matches that ofa known substance. Have you ever forgotten someone’s name and described characteristics of that person to a friend until they put all that information together to identify who you are talking about? This is an example of qualitative analysis. In chemistry, we collect characteristics about the reactivity of an unknown ultimately allowing us to identify the unknown substance. Each chemical test (reaction) leads to observations. As you can imagine, to be sure about the identity of the unknown, once we identify a chemical qualitatively, we must confirm it using multiple methods. Sometimes, these confirmatory analyses may be quantitative (e.g. density, molar mass, amount that reacts with a given amount of other reactants, etc.).

In recent years, NASA has sent several probes through our solar system; for example, Curiosity and MAVEN (Mars Atmosphere and Volatile Evolution) were sent to explore Mars. How can we make inferences about the composition of our neighboring planet’s soil and atmosphere? Who develops the methods used to explore our solar system and who runs the tests?

As you can itaagine, this information has the potential of changing our fundamental understanding of our universe!

2. PROJECT DESCRIPTION

Despite efforts to rapidly stop the oil spill in the Gulf of

Mexico and to minimize the damage, a wide region of the Gulf was severely affected, Years later, the Gulf ecosystem, nearby coasts and water, still show the consequences of the oil spill. Fortunately, governmental authorities such as the Environmental Protection Agency (EPA) continuously monitor water samples collected from the Gulf of Mexico. Abnormal levels of certain inorganic

Figure 1 : Oil spill Gulf of Mexico

Published January 12, 2014 in Gulf Qeep.yatec

contaminants may represent a concern because of their

effect on marine organisms. Not all pollutants may come

from the spill though; industries along the Gulf Coast may also contribute. Knowing what inorganic contaminants may be present in Gulf water samples may help in determining possible sources and corrective actions (Figure 1).

The objective of this project is to determine inorganic contaminants present in water samples from different sources. Your team will be given a solid sample containing only one salt and using qualitative (such as solubility) and quantitative tests (volumetric and gravimetric analysis), you will find the identity of the unknown compound.

For inorganic compounds, such as your sample, chemists commonly use two methods, gravimetric or volumetric analysis. Gravimetric analysis is based on the measurement of masses (weights); whereas volumetric analysis is based on the measurement of volumes. Gravimetric analysis will be suitable for unknown compounds that form precipitates when reacted with certain substances. The precipitate can be filtered out from solution (Figure 2), air-dried and its mass can be

compared to the expected (or “theoretical”) mass of the Figure 2: Simple filtration www dvusd org product if your unknown is what you thought it was. You may be able to make inferences about the accuracy of your identification based on how similar the experimental and the expected masses are. Using this method requires understanding solubility rules, stoichiometry and chemical equations.

For example, let’s say you think your unknown is MgS04 and by using a solubility table, you decide to react it with BaC12:

MgS04(aq) + BaC12(aq) MgC12(aq) + BaS04(s)

Your choice of using BaC12 is based on using the solubility rules with which you can predict that one of the products will be insoluble BaS04, which should precipitate out of the solution. Using stoichiometric calculations, your team can figure out how much BaS04 you should get ideally (expected mass) if you start with let’s say 0.500 g of your unknown. Remember, this is just an example! Gravimetric analysis should be suitable for the following inorganic compounds in your list: MgS04, word image 2259 Na2C204, Na2C03, (NH4)2S04, and CaC12.

Volumetric analysis will be suitable for unknowns that have acidic or basic properties. So, if you think your sample is one of the following, you can consider this methodology: NH4Cl, this is an acidic compound that can be analyzed using a solution ofNaOH of known concentration. CHJC02Na, Na2C204, Na2COJ are basic compounds that can be analyzed using an HCI solution of known concentration.

A clear understanding of stoichiometry and chemical equations is also necessary for this project. As an example, let us imagine your team thinks your sample is NH4Cl. Since this is an acid, you will want to react it with a standardized solution of base, NaOH (“standardized” means that you know the concentration of the solution). So, the chemical equation describing the reaction would be:

NH4Cl(aq) + NaOH(aq) NI-13(aq) + NaCl(aq) + 1-120(1)

With gravimetry, if you know how much of the unknown you are using for the reaction, let’s say 0.500g, your team should be able to determine how much of the titrant (in this case NaOH) would be necessary to complete the reaction. Comparing the volume actually used (experimental) and the expected (calculated or theoretical) volume will give you information to make inferences about the accuracy of your identification! You can determine in the lab some of the chemical and

physical characteüstics of your unknown like: pH, conductivity, solubility, burning color appearance, reactivity and physical appearance. Those characteristics will provide you with enough information, so your team can decide which chemical is your unknown. During your research, look for the theoretical values or characteristics of the chemical you think you have and compare what you find to the results obtained in lab.

PLANNING YOUR PROJECT: During the first week of this project, your team will identify the unknown inorganic compound using qualitative analysis. Your TA will give your team one unknown solid sample to work with. This is the entire sample. Do not waste it! The inorganic compounds listed below are the major targets for the identification analysis, These compounds will be available in the lab in case you need them:

calcium chloride (CaC12), sodium nitrate (NaN03), ammonium sulfate ((NH4)2S04), ammonium chloride (NH4Cl), magnesium sulfate (MgS04), calcium nitrite (Ca(N03)2), sodium acetate (CH3C02Na), sodium carbonate (Na2C03), sodium oxalate (Na2C204)

When using a technique for the first time, try it out using known compounds available in the lab to become familiar with the technique before using your unknown sample. When running reactions and tests, use small amounts of chemicals. Safety precautions dictate the use of small quantities of reactants for qualitative and quantitative analysis.

The second week, your team will run at least one quantitative test to confirm the identity of your unknown. Depending on the properties of the unknown compound that you find during the first week, you can either perform a gravimetric or volumetric analysis.

Answer the following questions before you start your experiment:

  1. Can you organize your procedures into a flow chart, isolating each chemical listed above through a series of tests?
  2. We already know that your salt is soluble in water. Would testing its solubility in other solvents (e.g. acid, organic solvents, such as acetone or alcohol) tell you anything about your compound?
  3. Solutions of many inorganic compounds are good conductors of electricity. How can you find out if your unknown compound conducts electricity? And if it does, how does it compare to other known compounds available in lab?
  4. physical characteristics can you use to compare your unknown compound with knovm compounds?
  5. How can you determine if your unknown compound has acidic or basic properties?

3. CON CEPTS AND TECHN IQUES

Other topics may need to be reviewed depending on your experimental decisions. It may be the case that some of these topics are new to some members of your team: solution.

concentration, stoichiometry, solubility, precipitation reactions, concentration of solutions, acidbase reactions, and random and systematic error.

In addition. revievång the folloyÅng techniques before coming to the lab will make work easier and more productive: analysis of ions (cation/anion), solubility test, flame test, conductivity test. gralämetric analysis, measuring volumes at different levels of accuracy, and titration. Consult the Laboratory Toolbox and the online resources provided for reference.

Sometimes, when we handle a substance it is easier to use it in solution. If you use solutions, make sure you understand the concentration units given. That will eventually help you with stoichiometric calculations. When you run reactions and tests, be sure to use small amounts of chemicals.

4. SUPPLE M ENTAL INFORMATION AND ONLINE RESOURCES

These links provide information about: concepts, research connection and /or laboratory techniques. Do not limit your search of information to these resources only.

  • USF Laboratory Toolbox: https://wvsw.usf.edu/artssciences/depsartments/chemistry/undergrad/teaching-labs/index.aspx
  • Stoichiometry:

http://chemwiki.ucdavis.edWAnalqical _Ch emistD /Ch ions/Stoichiomet Q’_a nd Balancing Reactions

  • Types of error:

http://chernvviki.ucdavis.edu/Anal)tical Chemistry/Quantifying Nature’Significant Digit s/Uncertainties in Measurements

  • Solubility: htt s://en.wikibooks.o -iki, General Chemist ‘{Solubility

word image 2260Flame test: http.//chemistry.about.com/od/analyticalchemistry_/a/flametest.htm

word image 2261 Principles of conductivity: https://www.youtube.com/watch?v=5qxeni3NpE0 word image 2262 Common Laboratory Tests: http.•//myu.rsc.org/learnchemistry/resource/res00001418!laboratory-best-practices?cmpid=CM POO()02777 word image 2263 The New York Times: Tracking the Oil Spill in the Gulf:

htlp://wvvn,v.mtimes.com/interactive/2010/05/01 /us/20 100501 -oi I-spill-tracker.html

5. SAFETY NOTES

You may be asked to leave the laboratory if you do not abide by safety norms:

  • Laboratory coat, splash proof goggles and gloves MUST be worn during this experiment. word image 2264 Wash your hands thoroughly at the end of the experiment.
  • Water is not a chemical hazard; however, other chemicals you may _propose to use in your experiments may present hazards. Consult the SDS (Safety Data Sheet) for each chemical; some chemicals may irritate/burn eyes and skin.
  • Do not pour any of your solutions or samples down the drain. Use the proper waste containers (solid. liquid waste).
  • Use small amounts of reactants, most qualitative analyses are done in small test tubes (if unsure, consult with your TA).

6. BASIC AVAILABLE MATERIALS

The following will be available in the laboratory. You will need to ask your TA for word image 2265 authorization before using any substance or equipment not listed here:

  • General laboratory glassware (Erlenmeyer flask, beaker, test tubes)
  • Conductivity meter or Multimeter
  • Bunsen burner e pH strips
  • Wire loop
  • Chemicals: calcium chloride (CaC12), sodium nitrate (NaN03), ammonium sulfate

((NEL)2S04), ammonium chloride (NHACI), magnesium sulfate (MgS04), calcium nitrate word image 2266 sodium acetate (CH3C02Na), sodium carbonate (Na2C03), sodium oxalate word image 2267 sodium chloride (NaCl), hydrochloric acid (MCI), sodium hydroxide (NaOH), ethanol (C2H60), acetone (C3H60), barium chloride (BaC12), silver nitrate (AgN03)

7. GUIDING IDEAS AND PLANNING OUESTIONS FOR THE PROJECT

Your team will get a small amount of an unknown sample, use it wisely. The following questions will guide you to prepare a plan for your project work. Some of the following items will require writing your ideas in your lab notebook; others are just for group discussion. We encourage students to use the web, textbooks, the USF Laboratory Toolbox, etc. during this planning phase. Check your planning with your TA before you leave the lab. If there is a test you want to run, you should outline a detailed procedure for it. Remember that tests may need to be run more than once to check the reproducibility of results, thus you need to manage your time in the lab as well.

  1. What safety protocols need to be followed for this project? What are the specific safety concerns for each chemical used? Consult the SDS for each.
  2. How will you test the chemical reactivity of your compound? How will you know if a reaction takes place?
  3. How will you use the available compounds to help you find/verify the identity of your unknown?
  4. Based on what you know about your unknown sample, which method would be more suitable, gravimetric or volumetric analysis?
  5. What balanced chemical equation describes the reaction of your unknown with the other substance you are using for this analysis?
  6. How much of your sample will you use for each trial? If needed, consult with your TA. How many trials do you plan on running?
  7. How will you prepare your unknown compound for the quantitative analysis? Will you use it as a solid or will you first dissolve it?
  8. How will you perform the quantitative analysis of your unknown? What will be the steps of this procedure and what data will be collected? Check the Lab Toolbox for further insight.
  9. Given the amount of unknown sample you decided to use: how much precipitate will form (if doing gravimetry) (this corresponds to the “theoretical yield”)? What volume of titrant will be

consumed (if doing volu:netry)? How will you use these results to confirm the identity of your compound? What sources of enor may affect your results?

S. PROJECT SUMMARY

At this point you should have a good idea of what your unknovan compound is or at least identify a good number of properties. Address the following questions based on your results:

  1. What is the identity of your unknos\n? If you have not yet identified it, V\hat compounds are close in physical and chemical properties?
  2. What experiments and tests did you carry out to determine the identity of your compound? How did each experiment contribute to its identification?
  3. How did you use the kli0NM1 compounds to support your ideas about the identity of the unknoysn?
  4. Calculate the percent error for the quantitative analysis you used as confirmation of the identity of your unknovsn compound.
  5. What sources of error could have affected your experimental observations and measurements? Can these sources of error be eliminated? What effect (quantify) may your error have on the results?
  6. What are the limitations of the equipment and processes you used? Propose changes to the experimental procedure that address those sources of error,

As soon as it is time to plan. clean and put away all chemicals, materials and glassware promptly so that you get to complete these important tasks.

9. THINGS YOU MAY WANT TO CONSIDER FOR YOUR PROJECT

word image 2268 Whether you are giving a poster/oral presentation or writing a formal lab report, be sure to present your experimental data in an easy-to-read/follow format. Always include the appropriate units for measurements and significant figures. Consider describing general aspects and findings from your study of physical and chemical properties of the unknown, as well as the known compounds. Focus on the most significant experimental observations and results that helped you confirm the identity of the unknovm compound. Avoid wasting time with superfluous information.

Do not overemphasize procedures that you know other teams performed. Focus on the steps you think are unique to your team. For example, how did you perform the confirmatory, quantitative analysis and why did you choose to do it that way?

When you discuss your findings, make sure your claims are well supported by your experimental evidence. In all scientific investigations, results are subject to error. Can you think of sources of error that affected your observations and results? Could these sources of error point you to a false identity for your unknown? Were there other compounds on the list that could reasonably have been your unknown?

Remember we want you to connect your experimental work to science research and applications. What similarities do you find between your lab work and what you know about science research and applications? How does your experiment/research apply to the world outside of the university?

word image 226910. RESEARCH CONNECTION

word image 2270 Commonly, researchers in chemistry and interdisciplinary fields study new materials from a variety of sources. While some researchers focus on designing new chemicals with desired properties, others take samples from the environment and study them to understand their chemistry and potential uses. The latter approach is the approach Dr. Bill Baker’s lab group takes. His research is focused on the analysis of chemical compounds present in marine organisms. Some of the target organisms that his group studies are native from the Gulf of Mexico and the Florida D coast, whereas others come from Antarctica. The following is an excerpt from Dr. Baker’s website: “Nature is an important source of new pharmaceuticals. Compounds that an organism has developed for its own defense can be used for man’s defense as antiviral agents (AIDS, Herpes), antineoplastic agents (cancer), or other pharmaceuticals. In collaboration with pharmacologists, we screen our new isolates in assays that will identify their potential as drugs” (htlp://chemistry.usf.edu/faculty/baker/).

Dr. Baker’s research group found one particularly interesting chemical, meridianin A, in the Antarctic tunicate Synoicum sp. Baker’s group found this chemical possesses remarkable biological activity and toxicity toward murine tumor cell lines. The discovery of this compound motivates Dr. Baker’s research group to explore the synthesis of analog compounds and to examine the analogs’ potential pharmacological effects and applications.

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