Rat Law Determination of the Crystal Violet Reaction

The concentrations and absorbances of the red and blue dyes were used to find the concentration of the purple dyes. From the graph of the blue dye, the linear equation for absorbance was y = mx + b. From that formula came the equation y = 7.915 x 104 (x) + 0.02489, where y represents absorbance, m is slope, x is concentration/molarity, and b is the constant/y-intercept. The same set up was performed for the red dye, but the equation produced was y = 1.045 x 104 (x) +.001298. The equations found when graphing absorbance vs. concentration were used to find the concentration of the purple dyes. The absorbance for purple dye 3 on the red wavelength of 470 nm equaled 0.149 and 0.818 for the blue wavelength of 635 nm. For purple dye 1

With these absorbance numbers a concentration curve was constructed and the unknown solution was determined by finding the point of absorbance on the curve.

10 microliters of the sample is then added and the assay absorption is measured at 340nm. If absorbance was above 1.5, samples were diluted.

The procedures for experiment A, B, and C all start the same. The first step is to put on goggles and get the data collection device set properly. The labquest needs to be plugged into the colorimeter accurately so that a click is heard when putting it in. The labquest needs to be reading digitally and the colorimeter needs to be set to 635 nm. Then shake the chloroplast solution and take a clean cuvette and fill it with 3 mL of distilled water, 3 drops of the chloroplast solution, and cap it. This is used as a blank to calibrate your labquest. Double check that the labquest is reading absorbance, this assures that the colorimeter is plugged into the labquest accurately. Insert the blank into the colorimeter and hit the calibration button. Take out the blank and empty it. The labquest is now set to experiment with. Make sure that the heat bank is set in front of the lamp and that the lamp is on. The cuvette must be placed on the opposite side of the heat bank in the path of light in the box so that no other light can interfere with the experiment.

The ending result of this experiment confirms that as five test tubes are lined up with the varying level of absorbance, different results in the level of absorbance will appear as well, this is visible in above table. Thus, this is due to the varying amount of water in the solution. The blank sample had a 0.30 in its level of absorbance.

Time) because it had a correlation closest to 1. All three orders were graphed and a linear regression was used to see which graphed order was closest to 1. The order was determined by comparing the concentration and time to the mathematical predictions made using the integrated rate laws. Analyzing each graph and finding each correlation helped determine which graph was closest to 1. The more concentrated a solution is, the higher the absorbance of that solution. This is due to Beer’s Law. The law measures the absorbance of a solution by determining how much light passes through a solution. As the concentration of a solution increases, fewer wavelengths of light are able to pass through the concentrated solution. The absorbance at 60 seconds was 0.573 (Figure 1: Table1). To calculate the concentration (molarity), the Beer’s Law equation was used, Abs = slope(m)+b. Plugging in what is known into the Beer’s Law equation resulted in 0.573 = 3.172e+004 + 0, where the concentration is determined by M = 0.573-0/ 3.172e+004. So, the concentration at 60 seconds using the equation (M = 0.573-0 / 3.172e+004) was 1.824e-5 M. The 1st order graph resulted in k=0.006152 (Figure 1: Graph 1). Other groups also resulted in their decolorization of CV to be the 1st rate

The Beers Law calibration experiment used many concentrations of crystal violet solutions. Each of these solutions were test and analyzed in order to determine the absorbance of each concentration The results were than graphed and produced a slope of 1.00E05 with an intercept of -2.21E-02.

Each stock solution was placed in a colorimeter and was tested for it Absorbance. A computer program tested and drew up the Calibration curve/linear fit equation. However, the computer could not protect potential errors. An error for determining the concentration of the diluted and undiluted, could be a skew linear fit equation. The linear fit equation could be skewed by having an inadequate ratio of the stock solution and distilled water. For example, when making stock solution 1, 0.021(L) was used instead of 0.020(L) can throw the calibration curve, resulting a skewed linear fit equation. If the “blank” was not fully clean or had left over Allura Red residue, then the “blank” was tampered with. A tampered “blank” means any comparisons with it would have a wrong Absorbance reading. However, the most likely and most effective error, is calculation. Using the wrong V1 and V2 to determine the concentration of the undiluted would affect the answer of the grams Allura Red would be consume and the amount of molecules of Allura Red. The colorimeter is adjusted to a wavelength of 470 nm is maximize the absorbance of the Allura Red. If wavelength was place at 565 nm, then Allura Red would not absorb as much color of

The dark, navy blue colored graph represented the absorbance curve for the S1 sample. The red colored graph represented the absorbance curve for the S2 sample. The green colored graph represented the absorbance curve for the P1 sample. The purple colored graph represented the absorbance curve for the P2 sample. The gaps between the P2 curve was due to the oversaturation that led to the inconclusive spectrophotometer readings. The blue colored graph represented the absorbance curve for the P1 low salt sample. The orange colored graph represented the absorbance curve for the P2 low salt sample. The light blue colored graph represented the absorbance curve for the P1 medium salt sample. The light pink colored graph represented the absorbance curve for the P2 medium salt sample. The light green colored graph represented the absorbance curve for the P1 high salt sample. The light purple colored graph represented the absorbance curve for the P2 high salt

The values of color absorbance are effective because color absorbance has a linear relationship with concentration values, which in turn, allows us to easily find concentration values for many solutions. Beer’s law describes this phenomenon since the absorbance is directly proportional to concentration. We observed that as the color absorbance increased, the concentration of the FeSCN2+ complex ion increased. This is because as the FeSCN2+ concentration increases, the blood-red color becomes darker due to more presence of the blood-red FeSCN2+ ion. Therefore, the color absorbance increases because there is more blue color absorbed by the darker red color. We then graphed the absorbance and concentration values and created a line of best fit. Using the line of best fit, we were able to predict the equilibrium concentrations of the FeSCN2+ solutions and find the change required to reach equilibrium. Since we already knew the initial concentration of FeSCN2+ and since we already found the equilibrium concentration of FeSCN2+, we can calculate the change in equilibrium. Using this data, we were able to calculate the equilibrium concentration of all of the species in this lab, since we already knew the change from the initial concentration to the equilibrium change. Q is less than K because there was no initial concentration of FeSCN2+, but after the system reached

b. Describe the spectral curve of each target type with respect to its absorption and reflectance characteristics. (3)

A = Absorbance difference  = Molar extinction coefficient C = Concentration L = Path length

3. The spectrophotometer was set at 420nm. Distilled water was also used as the ‘blank’.

The absorbance is measured using a Plate reader and a Standard curve is generated. Also, the different types of pipetting techniques are assessed in this Assay.

3 because this is the maximum absorbance for the iron (III) ion. The Beer's Law Plot that was graphed came out to be linear with an equation of: