The Determination of an Equilibrium Constant Objectives: The objective of this lab is to find the equilibrium constant of Fe(SCN)2+ through multiple trials using a spectrometer. Since one chemical is colorless and the other is colored a spectrometer can be used to monitor amounts of each in the solution. By completing multiple trials an average can be reached for the value of the equilibrium constant of Fe(SCN)2+. Procedures: To complete this lab several chemicals must be measured and transferred to test tubes. First 5.0 mL of 0.200 M Fe(NO3)3 must be diluted to a total volume of 50 mL in a flask. Next 0.0020 M SCN–. This solution is then added to 4 test tubes in 1 mm increments. Each test tube is then put in to …show more content…
cuvets and tested in the spectrometer at 420 nm and the absorbance is recorded. In the second part of this lab the same process will be used but with different amounts of substances. This time the 0.0020M Fe(NO3)3 and SCN–. Three test tubes will be filled with 3.0 ml of Fe(NO3)3 and two more will be filled with 3.0 ml of the substance. Each set of three test tubes will be filled with 3.0 mL increments of SCN–starting at 1.0 ml and ending at 3.0 ml. The test tubes will then once again be given equal volumes by adding the required amount of HNO3. The solutions will once again be transferred to cuvets and put in a spectrometer at 420 nm. Once their absorbance has been recorded the procedures are complete. Conclusions: This lab was very extensive and clearly demonstrated the process of determining equilibrium constant.
After working through many calculations I came out with an average constant of 280, an accurate measurement. Although my readings caused me to have an accurate final answer, they were not precise. My values for the equilibrium constant varied greatly in some of ten trials, ranging from a low of 260 to a high of 320. Other contributions to the value of the constant would be the accuracy of the measuring devices, the purity of the solution and the accuracy of the best-fit line drawn on the graph. Since one of these solutions is clear and the other is colored their Concentrations can easily be found. The solutions can be simply put into a spectrometer and the absorbance will reveal how much of the colored solution resides in the solution. Your results in part one of the experiment can be used to create a graph with which you can make a best fit line and find values for the absorbencies in part two. This information can then be used to calculate the equilibrium constant in all or ten trials and an average can be taken. It allows the student to view first hand exactly what happens at equilibrium and then put this knowledge to
use.
The essential points of the green-frosting are the concentration and absorbance value in each diluted which the process of serial dilution. The standard curve of Blue#1 and yellow #5 provide the equation of the trend-line in order to calculate the concentration in the diluted solution of the green frosting. The mole of dye in 100mL green stock solution, mole of dye in 5 gram and 1 gram of frosting, the Beer –Lambert Law, and the compare to amount desired by the company can be determined. The Beer-Lambert Law is the relationship between color and the concentration and equation A=Ebc. The “A” is absorbance, the “C” is a concentration in molarity, the “E” is a molar absorptivity and “b” is the path-length. The goal of the lab is to use the absorbance and the Beer-Lambert law to determine the amounts of blue#1 and yellow #5 in the green frosting.
2. Cooper, M. M., Cooperative Chemistry Laboratory Manual, McGraw-Hill: New York, NY, 2009, p. 60.
Using the calorimeter, we firstly needed to calibrate the machine; to do this we took a tube of distilled water and tested it; we knew that this should measure 0 because distilled water is completely transparent. We could have done this with any known reference sample. Once we had calibrated the machine we could then test the real samples for their transparency, we tested all five of these samples a total of three times each. Between each different concentration of solution sample we had to re calibrate the machine using the distilled water again, so in total we did 20 colourimetry tests. We gained three results for each concentration of sample and then calculated an average from these three results; these are shown in the table below.
3.) Divide your 30g of white substance into the 4 test tubes evenly. You should put 7.5g into each test tube along with the water.
of each in each test tube. (Table below showing how I am going to make
the water baths I think were accurate enough but having two thermometers in each bath maybe would have helped to hold the temperature readings more accurately. We were not given any instructions either to shake or not to shake the test tubes with the coloured solutions before inserting them in the spectrophotometer to read the absorbance. By shaking each test tube a certain number of times before putting it in the spectrophotometer could have improved the accuracy of the absorbance of the solutions.
Taking this away from the total amount of acid = 1.55 x 10-3 - 0.1 x
Before beginning the experiment observe and record the physical appearance of all the chemicals used in the experiment. First write a balanced chemical equation that has Zinc iodide as product when Barium iodide and zinc sulfate are used. To begin today’s lab, weigh a small test tube on a scale that goes to the hundredths place. Using a clean spatula add .45 g + .03 grams of zinc sulfate heptahydrate (.25 g + .03 grams if zinc sulfate is used) into the small test tube. Dissolve the sample in 2 mL of deionized water. Make sure al of the powder is mixed with the water, stopper the test tube and shake for about 1 to 1 ½ minutes to dissolve. Let the test tube stand and weigh another small test tube. Depending on what is being used, .61 g +.03
The calibration curve shows the absorbency with varying concentrations of a blue dye water mixture. Beers law (A= e b c) suggests that by connecting the points on the graph, a straight line should occur because absorbance is proportional to concentration1.The equation at the top of the graph was used to calculate the amount of dye in the actual PowerAde solution. The absorbency of the blue PowerAde was taken from the spectrometer as 0.56. By putting 0.56 into the formula as y, determining the concentration was as of simple as solving for x. By looking back at figure 2 it was determined that a concentration of 5.1x10-6 moles falls between test tube 4 (40% concentration and 3.9x10-6 moles) and test tube 3 (60% concentration of the dye and 5.9x10-6 moles) therefore we can conclude it is in the middle of these two concentrations approximately 51% concentration. This shows that approximately 51% of blue PowerAde is dye and the other 49% is water and other substances. The results also suggest that because the mixture was transmitted as a blue color, the absorbed color would have been orange, it's complimentary color. It can be concluded that the max wavelength absorbency corresponds to a particular color that is transmitted from a substance the color we see, however the color that is absorbed is always its complimentary
The purpose of this lab is to use lab equipment and procedure to gather data about the mass of an undefined amount of magnesium and oxygen. This data is then meant to be used to find the empirical formula of a magnesium oxygen compound.
== § Test tubes X 11 § 0.10 molar dm -3 Copper (II) Sulphate solution § distilled water § egg albumen from 3 eggs. § Syringe X 12 § colorimeter § tripod § 100ml beaker § Bunsen burner § test tube holder § safety glasses § gloves § test tube pen § test tube method = == = =
tube. Add 6 mL of 0.1M HCl to the first test tube, then 0.1M KMnO4 and
The purpose of this experiment is to use our knowledge from previous experiments to determine the exact concentration of a 0.1M sodium hydroxide solution by titration (Lab Guide pg.141).
Five clean and dry test tubes are obtained and labeled 1-5. Each is filled with exactly 2.50 mL of .200 M Fe(NO3)3 using a burette. Then 0.50 mL of 0.002 M KSCN solution is added to test tube 1. 0.75 mL of 0.00200 M KSCN is added to test tube 2 and so on in increments of 0.25 mL. Finally, enough 0.5 M HNO3 is added to each test tube so that the final volume is equal to 10.0 mL. Each test tube is mixed and then the contents of each are added to a cuvette and tested within a spectrophoto...
The three variables that are to be investigated in this particular experiment are temperature, concentration and a