CHM 114 Study Guide - Final Guide: Molar Attenuation Coefficient, Phenanthroline, Transmittance

177 views2 pages

orchidyellowjacket836

31 Dec 2016

School

Department

Course

Professor

For unlimited access to Study Guides, a Grade+ subscription is required.

Document Summary

Purpose: in this experiment we determine the concentration of fe2+ in an unknown solution. We will determine this by using a spectrometric analysis of different solutions and compare. Theory: when iron is introduced with the ligand (1,10) phenanthroline, a complex is formed to exaggerate the color of the sample to be able to apply beer"s law to determine the concentration of iron. We use a spectrometric approach to determine the absorbance of different samples of. We know the path of light length is a constant of 1 cm and that the molar absorptivity is also a constant with comparison. From this we can determine concentration directly from absorbance. We can then plot the absorbance vs concentration and determine the concentration of the unknown sample on the line of best fit. Beer"s law: a=ebc (absorbance= molar absorptivity x length of light traveled x molar concentration) Equations: (ml fe2+)(50 ppm) = (x ppm)(100 ml) Table 1: ppm vs absorbance at different concentrations.

Related Questions

Spectrophotometric Determination of Iron in a Vitamin Pill Introduction Iron is one of the essential elements in the human diet. In the body, iron is present in the form of dietary iron results in the condition of anemia. Many people take vitamin pills containing iron to supplement their dietary intake ofiron. The technique of is method of instrumental analysis. Many different types spectrophotometers are available that a of the electromagnetic radiation transmit light in different regions spectrum. In is experiment, a visible spectrophotometer will be used. A visible spectrophotometer of a measures the amount of light that a colored solution absorbs. When a beam o the sample depends on wavelength passes through a colored solution, the amount of light absorbed by the concentration of what the substance is that is absorbing the light. The absorbance also depends on the the path through the light passes. The relationship between absorbance, concentration, and pathlength is expressed by the equation known as Beers la gte where A is the al of the solution, E is a constant called absorptivity, which is a characteristic of the substance and the wavelength of the absorption, c is the concentration of the absorbing substance in is a unitless the solution, and e is the length of the path through which the light passes. Abe quantity, concentration can be expressed in any convenient concentration unit, and the pathlength is measured in centimeters. The units of absorptivity depend on the concentration units used. In this experiment concentration is measured in mg/mL Therefore, the units of e are mL/mg cm To determine the absorptivity of a particular substance, a calibration curve is constructed. A series of standard solutions in which the concentration of the absorbing species is known are prepared and their absorbances absorbance as a function concentration is made. If the absorbin species obeys Beer's law, the plot will be a straight line, y mr b. When the pathlength is 1.0 cm, the slope of the line is the absorptivity. The absorbance of a solution of unknown concentration can be read and its concentration determined from the calibration curve. In this experiment, a commercial vitamin pill will be analyzed for its iron content. The form of iron present in the vitamin pill, most likely iron(T) sulfate, has a negligible visible absorbance. The iron(T) will be converted to a species that has a large absorbance, allowing the absorbances of solutions of low iron(T) concentration to be measured. The reagent 1.10-phenanthroline, Figure 1, reacts with is red-orange and absorbs visible ligh most strongly at 508 nm. Iron(ll) is easily oxidized to iron(TI) in aqueous solution. A reducing agent, hydroquinone, is added to the solution to prevent this oxidation from occurring. In addition, the acidity of the solution must be controlled to ensure the formation of the complex. In this experiment, sodium citrate is added to maintain the proper pH of the solution A series of standard solutions with known iron concentrations is prepared, the absorbances of the solutions are read, and a calibration curve constructed. From the calibration curve, the concentration of iron in a solution made from the dissolved vitamin pill will be determined and the total amount of iron in the vitamin pill calculated.

CHM 114 Study Guide - Final Guide: Molar Attenuation Coefficient, Phenanthroline, Transmittance

Document Summary

Get access

Related Documents

CHM 114 Study Guide - Final Guide: Chemical Kinetics, Cuvette, Phenolphthalein

CHM 114 Study Guide - Final Guide: Complexometric Titration, Murexide, Ethylenediaminetetraacetic Acid

CHEM-UA 126 Study Guide - Final Guide: Ni Ni, Buffer Solution, Potassium Iodide

Related Questions