Effects Of Concentration On The Absorbance Values

Effects Of submergence On The Absorbance ValuesAbstractA 0.2100 M germinate tooth root of carbon monoxide gas (II) chloride hexahydrate was open firevass apply UV-Vis spectroscopy. A series of dilutions of the comport origin were do to analyze the effects of minginess on the absorbance set of cobalt (II) chloride hexahydrate apply the UV-Vis spectrophotometer. The bullshit (II) chloride hexahydrate was effect to begin the highest absorbance value at an average wavelength of 511.02 nm. The average milling machinery extinction coefficient for copper (II) chloride hexahydrate was found to be 4.5172. spectroscopical analyses of dilutions of the origination ascendent were apply to pee-pee a normalization coil of absorbance versus concentration of the cobalt chloride hexahydrate solution. A solution of outlander concentration was analyse utilize the UV-Vis spectrophotometer. The calibration curve was used to intend that the unknown had a concentration of 0.1250 M.IntroductionUltraviolet/Visible (UV-Vis) spectroscopy analyzes electronic transitions surrounded by atoms and molecules. Spectra are produced when electrons in molecules or atoms move from one electronic vim level to an different of higher energy. In doing so, the absorbed energy is compeer to the difference between to the two levels. Compounds that absorb airy in the patent region are colorise. Compounds that absorb clean-cut only in the ultraviolet illumination region are colorless.Inside a UV-Vis spectrophotometer there are usu all(prenominal)y two light sources, a tungsten lamp for the visible region (380-800 nm) and a deuterium lamp for the ultraviolet region (10-380 nm). The light source produces a fair light ray which contains all wavelengths (all colors). The light ray directed to a monochromator by a mirror. The monochromator is used to separate light into specific wavelengths. distributively wavelength corresponds to a different color. The instrument scans thro ugh the UV-Vis spectrum, sending different wavelengths of light through the try on. A single wavelength passes into the modulator, which consist of a rotor with mirrors that splits the light into two beams. One beam passes through the sample cell, while the other passes through the reference cell. Both sample and reference beams are redirected by mirrors into a detector. The detector compares their intensities of the two beams and sends a taper to the computer that controls the instrument. The signal is defined as absorbance, which is a measurement of how much light is macrocosm absorbed by the sample at that particular wavelength.The Beer-Lambert law states that absorbance (A) is pro partate to concentration of the absorbing species and fashion length of the medium over a certain timeIn equation 1, is the molar extinction coefficient and has units of, the path length of the medium or L, is reassured in centimeters or cm and the concentration of the absorbing species has unit s of molarity or M.In this try out a solution of cobalt (II) chloride hexahydrate was analyzed using UV-Vis absorption spectroscopy. The purpose of this experiment is to create a calibration curve of absorbance versus concentration by reservation series of dilutions of cobalt (II) chloride hexahydrate. The calibration curve will accordingly be used to determine the concentration of an unknown sample. The molar extinction coefficient for cobalt (II) chloride hexahydrate will also be find using the absorption at the concentrations of from apiece one dilution.Experimental ProcedureUsing the analytical balance, 2.5072 g of cobalt (II) chloride hexahydrate were weighed and placed into a 50 mL beaker. The purple solid was change state inside the beaker using 15 mL of distilled water. The purple liquid was then transferred to a 50 mL volumetric flask with the aid of a funnel. The beaker was then rinsed with another 15 mL portion of distilled water to assimilate any remaining cobalt (II) chloride hexahydrate left behind and then was transferred to the 50 mL volumetric flask using the same funnel. Additional 20 mL of distilled water were added to the 50 mL volumetric flask to create the entrepot solution of cobalt (II) chloride hexahydrate.Dilutions of the stock solution were made by transferring 2, 4, 6 and 8 mL of the stock solutions to four labeled 10 mL volumetric flasks. Distilled water was added to fill each flask to the line.The absorbance for each solution was calculated using spectrophotometer. Before any samples were analyzed, a sample containing just water was used to place the instrument. A quartz cuvette was fill with distilled water and cover. The blank sample was placed in the sample bearer in the back of the spectrophotometer. Using the program, the spectrophotometer parameters were set to scan the sample from 650 nm to3 90 nm. The program was also designed to automatically let the user know which sample to place next into the sample holder.A fter the blank sample was analyzed, the cuvette was rinsed with distilled water first and then with a small portion of the stock solution. The cuvette was then filled with a portion of the stock solution, covered and analyzed using the spectrophotometer. This procedure was repeated for all dilutions. After each synopsis, the cuvette was first rinsed with distilled water and then rinsed with a small portion of the pastime sample.ResultsIn order to analyze the sample using the spectrophotometer, the compound necessarily to be present in the aqueous form. The copper (II) chloride hexahydrate appeared purple as a solid. After the 2.507 grams of copper (II) chloride hexahydrate were dissolved in 50 mL of distilled water, the compounds color changed from a dark purple to a pink colored solution.The concentration of the copper (II) chloride hexahydrate stock solution was found using the molecular weight of the compound, the amount of compound used and the amount of distilled water used to dissolve it. display panel 1 shows the how the concentration of the copper (II) chloride hexahydrate stock solution was found.When the dilutions were made by taking 8, 6, 4 and 2 mL of the stock solution, the concentration of each dilution decreased proportionally to the amount of stock being added. The intensity of the pink color of each dilution also decreased as the amount of milliliters of distilled water increased. tabulate 2 shows how the concentration for each dilution of the stock solution was calculated.The software was programmed to analyze the solutions in the following order, the blank sample, the stock solution (0.2100 M), the 0.1680 M dilution, the 0.1260 M dilution, the 0.0840 M dilution and 0.0420 M dilution. All samples were analyzed in the spectrophotometer, by using quartz cuvettes. The blank sample had no visual results as expected. When the 0.2100 M stock solution was analyzed by the spectrophotometer, the computers monitor displayed the formation of a c hart starting at 650.00 nm on the x-axis and 0.00 Absorbance on the y-axis. After the graph passed 580.00 nm, the graphs absorbance values started to increase exponentially. The maximal absorbance value was recorded at 0.9993 and it occurred at upper limit wavelength of 511.34 nm. After the was passed, the graphs absorbance values started to exponentially decreased until the graph reached 420.00 nm, after 420.00 nm the graphs absorbance values displayed a slightly constant pattern until the end of the graph at 380.00 nm. same results were observed for all the dilutions. The 0.16800 M dilution analysis showed a maximum wavelength of 510.92 nm and a maximum absorbance value of 0.7266. The 0.12600 M dilution analysis showed a maximum wavelength of 511.11 nm and a maximum absorbance value of 0.5703. The 0.0840 M dilution analysis showed a maximum wavelength of 510.98 nm and a maximum absorbance value of 0.4024. The 0.0420 M dilution analysis showed a maximum wavelength 510.75 nm and a maximum absorbance value of 0.1758. Table 3 summarizes all the maximum wavelengths and absorbance values for the stock solutions and all its dilutions. take in 1 (appendix-pg 14) illustrates the graph for each solution.Using the data from shelve 3, a calibration curve of absorbance versus concentration can be created. Figure 2, the calibration curve can be found in the appendix section, rascal 13.The molar extinction coefficient for copper (II) chloride hexahydrate can be found using data found in Table 3 and the Beer-Lambert law. By algebraically manipulating the Beer-Lambert equation (A = * L *c), the molar extinction coefficient () for copper (II) chloride hexahydrate can be determined by = A / L*c. The molar extinction coefficient for all the solutions can be found in Table 4. The average molar extinction coefficient for copper (II) chloride hexahydrate was found to be 30445.A solution of unknown concentration was analyzed using the spectrophotometer following the sam e procedure as all other solutions. The solution of unknown concentration was found to need a maximum wavelength of 511.49 nm and a maximum absorbance value of 0.5715. The concentration of the unknown sample was determined using the equation of the line found on the calibration curve (page 13-Appendix). The unknowns absorbance value of 0.5715 was used as the y-value and the equation was solved for its correspondent x-value or concentration. The unknowns concentration was found to be 0.80 M. Table 5 shows how the equation of the line from the calibration curve was used to determine the concentration of the unknown. Figure 3 in the appendix section-pg 14, is a graph of all the solutions tested. In figure 3, the unknown is easier to identify because the graph is in a landscape format and the x-axis increases by a factor of 20 nm as opposed to a factor of 50 nm in Figure 1.ConclusionThe spectroscopic analysis of copper (II) chloride hexahydrate made the students familiar with opera ting a spectrophotometer. Dilutions to a stock solution of copper (II) chloride hexahydrate were made to examine how different concentrations of the compound affected the absorbance values of each sample. The copper (II) chloride hexahydrate was found to have the highest absorbance value at an average wavelength of 511.02 nm. A calibration curve for the concentration versus absorbance of copper (II) chloride hexahydrate was created using the data obtained from stock solution and dilutions using the spectrophotometer. A unknown sample was found to have a concentration of 0.1250 M. The concentration of the unknown was determined by using the calibration curve along with the data obtained from the spectrophotometer. The average molar extinction coefficient for copper (II) chloride hexahydrate was found to be 4.5172. The value for the molar extinction coefficient was determined using the theory behind Beer-Lambert law and maximum absorbance values from the spectrophotometer. watchwordA different approach to determine the concentration of the unknown involves using the average molar extinction coefficient for copper (II) chloride hexahydrate found in table 4. By algebraically manipulating the Beer-Lambert equation a formula for concentration can be derived c =http//www.800mainstreet.com/elsp/Elsp.html