Calorimetry Lab

Different procedures were used to isolate benzil from the ether layer and benzoic acid from the aqueous layers. To isolate benzil, anhydrous MgSO4 was added to the flask containing the ether layer solution. MgSO4 removes the remaining water in the ether layer solution. After making sure that enough amount of MgSO4 present in the solution, the ether solution was filtered by using gravity filtration. During filtration, MgSO4 was removed from the solution and the ether solution was collected in 25 ml flask. To separate benzil from the filtered ether solution, the beaker containing the ether solution was heated until the ether evaporated. After letting the beaker to cool to room temperature, the mass of the beaker with the benzil crystals was measured. From the combined mass of the beaker and the benzil crystals and from the predetermined mass of the beaker, the mass of the collected crystals was calculated to be 0.266 gram.

After the serial dilutions of the red and blue dyes were taken, the molarity and absorbance for both dyes were calculated. Using the MiVi = MfVf equation, the concentrations for each value of the red and blue dye were separately calculated. Calculating absorbances calls for setting the correct wavelengths of light for each dye. In this case, the 470 nm wavelength for red dye and the 635 nm wavelength for blue dye was needed to find the maximum absorbances. The absorbance was found by blanking the colorimeter and entering the concentrations. After both values of the absorbances and concentrations were found, the values were then graphed in order to obtain the equation of the relationship between absorbance and concentration.

In this study, the use of an HPLC instrument with a UV/Vis detector to determine concentration of caffeine and benzoic acid in an unknown solution mixture will be evaluated by its ability to calculate these concentrations in Mountain Dew.

3ml of sample was taken first flask at 4 minutes and added to the appropriate tube of sodium hydroxide, from the second flask at 4.5 minute and so on, each flask was sampled at 30 second intervals. The sampling was then repeated starting at 8,12,16 minutes. The final sample from the last flask was taken at 18.5 minutes. Once the sampling was completed, measurements of absorbance were obtained for solution in each tube at 405 nm.

The isosbestic point of the acid (pH6) and basic forms (pH10) of para Nitrophenol (PNP) was expected at 350nm. As you can see in figure 2, the graph shows the intersection of 2 curves at ~350nm, which is matched with the literature value. Also, the pKa of PNP was expected 7.15 at room temperature. Refer to figure 3, the pKa is estimated to be 7.15-7.2, which very close to the literature value. In addition, the lab was succeeded in illustrating the use of a spectrophotometry to analyze concentrations of chemical substance. The absorbances of 2 unknowns were felt on the standard curve as the expectation (refer to table 4). The minimum absorbance of the known standards was 0.193 and the maximum is 1.830. The absorbance of the unknown

For this experiment, the amounts of Red 40 and Blue 1 were quantified in six different Kool-Aid samples through the use of a spectrophotometer. This was completing by performing serial dilutions on both dyes, Red 40 and Blue 1, and then creating calibration curves for each of the six samples. The absorbance and maximum wavelength values were obtained from the spectrophotometer for each individual drink sample. Beer’s Law was used to discover the concentration of

Three grams of a mixture containing Benzoic Acid and Naphthalene was obtained and placed in 100 ml beaker and added 30 ml of ethyl acetate for dissolving the mixture. A small amount (1-2 drops) of this mixture was separated into a test tube. This test tube was covered and labelled as “M” (mixture). This was set to the side and used the following week for the second part of lab. The content in the beaker was then transferred into separatory funnel. 10 ml of 1 M NaOH added to the content and placed the stopper in the funnel. In the hood separatory funnel was gently shaken for approximately one minute and vent the air out for five seconds. We repeated the same process in the same manner one more time by adding 10ml of 1M NaOH.

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

The goal of this experiment is to prepare a photosensitive solution and explore its properties. While analyzing the solution, one will learn how to successfully handle these sensitive chemicals and then establish its properties via spectrophotometry.

After 20 mL of methanol, 2.91 g of 2-naphthol, 1.71 g KOH, and a few boiling chips were combined in a small round-bottom flask and allowed to react, 1.8 mL iodoethane was added. The mixture was boiled for two hours with a reflux condenser; after adding 50 mL of cold water, the flask was sealed with a plastic stopper and parafilm and stored in a freezer for several days.

In the experiment, Luminol Synthesis and Chemiluminescence, the purpose is to create luminol using the base-mediated reduction of 5-nitro-2,3,-dihydrophthalazine-1,4-dione and to investigate the chemiluminescence reaction that luminol is known for. 5-nitro-2,3-dihydrophthalazine-1,4-dione was reduced using sodium hydrosulfite in a solution of sodium hydroxide under reflux conditions. Acetic acid was used to precipitate the solid luminol product, later the product was collected through vacuum filtration. The luminol product emitted a blue light when a dilute solution of it and sodium hydroxide was mixed with a dilute hydrogen peroxide and potassium ferricyanide solution. The blue light seen correlates to the excited molecules that are dropping

As the acid was being added, the mixture was being stirred over a stir plate. Once completed, the reaction mixture was poured from the round bottom flask into a 500 mL separatory funnel and its top (organic) layer was extracted into another beaker. The bottom (aqueous) layer was placed back into the funnel and extracted twice with 50.0 mL of ethyl ether each. The newly extracted layers were combined and dried over magnesium sulfate (MgSO4). The dried solution was the decanted into a beaker to remove the MgSO4 salts and the product solution was collected via Buchner vacuum filtration. The resulting product was transferred into an Erlenmeyer flask with an inverted beaker on top and stored in a drawer.

1 ml of water should be added to the first test tube and make a note. In the second test tube, 1 ml of methyl alcohol should be added. In the third test tube, 1 ml of hexane must be added. Lastly, the fourth test tube will be a control.

The boiling range of the 1-pentyl ethanoate distillate was approximately between 149-151°C. This was indicated by the formation of the distillate and when the mixture of the purified 1-pentyl ethanoate started to vigorously

Before any calculations, the spectra from the HCl solution and NaOH solution was verified to make sure that the wavelength at which the deprotonated form of 2-naphthol absorbs at 345 nm and that protonated form does not absorb significantly at the same wavelength. All the spectra in Figure 1 were baseline-corrected using the HCl solution spectrum, shown in Figure 2, and the NaOH solution spectrum was used to determine Amax at 345 nm.