Copper Sulfate Lab Report

Make sure to use the same type of cuvette to keep the width consistent and to prevent any experimental error from arising. Obtain 5 of the same type of cuvettes and pre-rinse them thoroughly. Label them numbers one through five in increasing molarity. Then, fill each of the cuvettes with one of the five solutions you created back in Part A. We will first examine the solution that exhibits the highest concentration or molarity. Make sure to wipe the outside of the cuvette with a Kimwipe before placing into the SpectroVis Plus device. Observe the graph that is generated and make sure to take note where the maximum absorbance takes place.

Potential error could result in when quantitatively transferring in any step and spillinng or not transferring all of any given solution. When diluting each flask has a different level for where its specific volume is, so overfilling the flask is possible when not being focused on. The condition of each penny can impact the results by if some copper was chipped off, or if anything attached to the pennies could impact test results. All of these could result in a different than desired copper percentage. It is important that the absorbance of each penny be within the range of absorbance the calibration curve has. This is because the curve created for this lab was made with 0.00 – 10.00mL of Cu^(2+)stock solution when using those values idealy this curve should therefore be 0-100% copper percentage. If values were found outside of this calibration curve then there would be problems with either calculations or a different curve would be needed to properly record

From this graph and chart we can see that the higher the concentration the higher the absorbance, all the different concentrations were tested at the same wavelength (625nm). Also we can determine our unknown substances concentration by using the absorbance we got for it. The red dot on the graph followed by the line towards the horizontal axis indicates that the concentration of fast green was 34% or 5.1x10-3.

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.

5. The degree of precision was to 3 significant figures obtained with the spectrophotometer. The major source of error in our experiment was not calibrating the spectrophotometer with distilled water.

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

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

XIII. Carefully remove the copper metal from the filter paper onto the watch glass. (with a spatula) Place a 400 ml beaker on a hot plate contained with water. Carefully place the watch glass before the water boils to dry the copper metal. (Use the tongs to handle the hot watch glass)

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.

Incorporation of assay controls included setting up a spectrophotomer and running the chart recorder with a full-scale deflection before the start of the assay. The set recorder had a corresponding value of 1 for the change in the absorbance. Therefore, prior testing was done to observe whether a change occurred in the readings. This helped to indicate that the results were valid, as they could have been affected by a fault during the setting up of the spectrophotometer. On the other hand this was considered as one of the controls for the experiment. Nevertheless, a new cuvette had to be used for each assay.

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

8) Steps 1 - 8 were repeated using the wavelengths of 360 nm to 900

concentration, record the absorbance readings at a fixed wavelength, and plot the absorbance vs. concentration data. The wavelength of 520 nm was selected for experiment Part

A possible error may be adding inaccurate amounts of buffer between samples, causing them to dilute either excessively or insufficiently, resulting in an inaccurate standard curve. Another error could be leaving the sample solutions for over 25 minutes, which could cause the protein to start degrading. Not zeroing the spectrophotometer or cleaning the tube properly can affect the absorbance value.

The same solution of 0.5 ml BSA was then added from test tube 1 to the test tube 2 after being properly mixed, and from test tube 2 the solution was being added to test tube 3, and so forth all the way up to test tube 5, with the same exact procedure. From the last tube, we then disposed the 0.5 ml solution. After above procedures, we now labeled another test tube “blank”; 0.5 ml blank distilled water was purred into the tube with the serial dilution of 1:10. We also had a tube C labeled “unknown” with the same 0.5 ml of solution. And after adding 5ml of Coomassie Blue to each tube (1-5) and to the blank, the result of absorbance was read at 595 nm.