Experiment 1: The Composition of Aqueous Complexes by UV-vis Spectrophotometry
CHEM 4310L Analytical Chemistry II
Call Section 100
Monday, Wednesday9:40-12:45
Joshua Holley, Kyle McQauid
01/22/14
Introduction
The purpose of this experiment is to determine the stoichiometry of a complex ion using Job’s method. In doing so, experience is gained in using the techniques and instrumentation involved in absorbance spectrophotometry.
When a metal cation (M) reacts with a ligand (L) a complex forms. The ligand acts as a Lewis base in the reaction and forms a coordinate covalent bond as the ligands lone pair goes to an empty orbital within the metal. To illustrate this: xM + yL → MxLy where x and y are stoichiometric ratios. To determine the ratios it is possible to use Job’s method. Also known as continuous variance, Job’s method carefully used reactant mixtures such that the total moles and volumes of reactants are constant [Harris, 2010].When just enough of the metal and ligand react the most product is formed. Measuring the absorbance of each solution, the absorbance can be plotted versus a mole fraction of metal or ligand. Using the two resulting equations the mole ratio can be determined. Absorbance is measured by ultraviolet-visible spectroscopy. This method uses visible light and ultraviolet light to excite an electron within a molecule. This will release a photon colored as what colors the molecule doesn’t absorb as the electron returns to its previous energy level. The UV-vis spectroscopic machine then uses this to measure absorbance [Misra 2002]. In this experiment, iron (II) will react with 1, 10-phenanthroline (shown below) to form iron (II)-phenanthroline. This reaction is shown as:
Fe_x^(2+)+phen_y→Fe_x...
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...roxylamine hydrochloride was left with the lid open when weighing out the appropriate mass to make the solution, and it is hygroscopic. There seemed to be some confusion on how to give the UV-vis machine a baseline. Negative values were given back on UV-vis which is unexpected.
Conclusion and Opinion
Overall, I enjoyed this lab even though there was a lot of down time and I look forward to the rest of the semester, but I wish people would be wary of contamination and the importance of washing and drying glassware before using it and after using it.
References
Misra, P. (2002). Ultraviolet spectroscopy and UV lasers. New York: Marcel Dekker.
Barlag, B. (2014) Quantitative Analysis II. CHEM 4310L Lab Procedure. Ohio
University
Harris, D.C. (2012). Quantitative chemical analysis. (8th ed.). New York: W.H. Freeman.
There were no significant error factors that may have affected the arrangement of the lab experiment. Everything went smoothly with relative ease.
The purpose of this lab was to analyse how light and color is created inside an atom in order to deduce what an unknown chemical compound was. We did two different experiments in order to examine how light is created and changed. In one, we looked at how chemical compounds affected a flame’s color, and to determine what the unknown salt contains. In the other lab, we looked at how atoms create light, and how it is displayed on the elements individual spectral line.
A cuvette was filled 3/ 4ths of the way and the absorbance measured in a spectrophotometer. The data was compiled as a class and recorded. The Spectrophotometer was blanked using a test tube of distilled water.
Optics Student Panel -Professional Development Activities During the student panel discussion held by the optics department, students (undergraduate, graduate and current professor) reflected on their experiences while here at the institute. The panel was conducted so that students could ask about graduate school, internships, and professional development within the optics major. Something special about the optics department is how they have Industrial Association, which is when members, faculty, and students connect with optics companies. With this opportunity, many panelists were able to receive jobs and addressed how they got hired, their internship/job experiences, and insight on what they did in their specific jobs.
There is also the potential of human error within this experiment for example finding the meniscus is important to get an accurate amount using the graduated pipettes and burettes. There is a possibility that at one point in the experiment a chemical was measured inaccurately affecting the results. To resolve this, the experiment should have been repeated three times.
Photosynthetic pigments are essential for life because they allow photosynthesis to occur by capturing sunlight which is then used alongside carbon dioxide and water to form organic compounds such as glucose and oxygen. The pigments allow the conversion of light energy to chemical energy which other organisms can benefit from. Oxygen is utilised by other organisms in aerobic respiration. The different pigments present in the chloroplasts allow a wide variety of wavelengths of light to be absorbed for efficient photosynthesis and provide colours to the plant to attract pollinators.
Individual atoms can emit and absorb radiation only at particular wavelengths equal to the changes between the energy levels in the atom. The spectrum of a given atom therefore consists of a series of emission or absorption lines. Inner atomic electrons g... ... middle of paper ... ... a sensitive multielement inorganic analyses.
Every day I went to work at the NYU laboratory or at Stevens Institute was an exhilarating and inspiring experience. I enjoyed the exposure of uncertainty in experiments that would arise in the lab multiple times throughout the weeks working in the facility. Nonetheless, the enigmatic feeling of coming across an innovative finding motivated me to work diligently. In my experience of working in the lab, I gratefully received training by the undergraduate students of my mentor, who were generous and elucidated me on how to follow the procedures in the lab and use the intricate equipment. Within a short time, I became adept with the intricate processes of the lab and was entrusted to carry on my own project independently.
According to (Biesen) , In a complexometric titration a coordination covalent bond is formed via the ability of most metal ions to receive unshared pairs of electrons from a anion or molecule. Furthermore, a ligand: which is a molecule that contain a lone pair of electrons and can therefore form a bond with a complex ion or metal ion. Therefore a ligand determines the metal ion concentration. [2] Therefore according to (Hussain, 2007), the maximum amount of ligands that can take part in a titration are known as Werner’s Number and allow for complex formation.[13]
- Take care when handling glassware eg. Thermometers, beakers, stirring rod and test tubes, to minimize breakage keep glassware away from the edges of the bench and be careful when holding and moving them around.
A Spectrophotometer is employed to measure the amount of light that a sample absorbed. The instrument operates by passing a beam of light through a sample and measuring the intensity of light reaching a detector. A Spectrophotometer consists of two instruments; one is a Spectrometer used for producing light of any selected color (wavelength) and second is a Photometer used for measuring the intensity of light.
Scattering takes place when obstacle dimension is smaller than wavelength of signal.Light scattering is a form of scattering in which light is the form of propagating energy which
It is mandatory that all the lab users need to work under the supervision of the instructor or any other qualified personnel. When conducting experiments, the users need to proceed with caution and report any spills, injuries and accidents to the teacher or the person in charge. The students should be careful when handling the lab chemicals and equipment to avoid accidents (Jay, 2010). When heating substances caution should be taken not to point the test tube to yourself or a colleague. All open flames that are in use within the lab should not be unattended and always turn off all the heating equipment and water taps when not in use. All the students should ensure that no experiment should be left while in progress at all
The mass spectrometer has long been an indispensable tool in chemistry. Molecules to be analyzed, referred to as analytes, are first ionized in a vacuum. When the newly charged molecules are introduced into an electric and magnetic field, their paths through the field are a function of their mass-to-charge ratio, mlz. This measured property of the ionized species can be used to deduce the mass (M ) of the analyte with very high precision.
In this experiment three different equations were used and they are the Stoichiometry of Titration Reaction, Converting mL to L, and Calculating the Molarity of NaOH and HCl (Lab Guide pg. 142 and 143).