Bromothymol Blue Lab Report

Procedure: I used a ruler, thermometer, and scale to take measurements. I used a graduated cylinder, short step pipet, scale, and ruler to determine volume and density. I used a volumetric flask, graduated pipet, pipet bulb, scale, and glass beaker to determine concentrations and densities of various dilutions.

In this experiment, the 5mM catechol (substrate) reacted with catechol oxidase in the presence of 5 different pH buffers mentioned above. This experiment was used to measure the buildup of the colored product, benzoquinone, to observe the change in the absorbance of the mixture in a spectrophotometer at a wavelength of 486 nm. Ithypothesized that since each enzyme has an optimal pH and that the enzymes are proteins, the enzyme activity will increase with pH level and will be at its highest at pH 7, which is water. As seen in figure 1, absorbance is low pH 2 because catechol oxidase activity was minimal at low pH concentration due to the catechol oxidase denaturing in the acidic solution. The catechol oxidases also denatured at high pH concentration such as pH 11, which is a basic solution, lowering catechol oxidase activity and absorption. Catechol oxidase activity was highest at pH 8 making it an optimal pH for catechol oxidase to catalyze the reaction and create more product which in turn increased the absorption of blue

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.

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.

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

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.

The purpose of this experiment was to determine the pKa, Ka, and molar mass of an unknown acid (#14). The pKa was found to be 3.88, the Ka was found to be 1.318 x 10 -4, and the molar mass was found to be 171.9 g/mol.

In the blank cuvettes, the 2 mL of pH levels 2,5,7, and 10 were added first, followed by the 1mL of peroxidase. However our experimental cuvettes contained both hydrogen peroxide and guaiacol. Before the cuvettes were placed in the spectrophotometer we added 0.1 mL of H202, followed by 0.02 mL of guaiacol these two substances were added last immediately before they were placed in the spectrophotometer. Para film was placed over the cuvette opening, and the assay solution was shaken and placed into the spectrophotometer where its saturation level was then tested. We recorded the saturation level of the solution every 15 seconds for 3 minutes. This process was repeated two times for each pH level for a total of two trials.

Table 2: Consists of color extract taken from a red cabbage for a natural indicator. The pH reading that was measured by using the pH meter and the result of the pH reading to determine whether the solution was acidic or basic.

The materials needed for this experiment included test tubes, a test tube holder, the unknown compound #202, 35mL beakers, gloves, safety goggles, ethanol (to clean equipment), stirrer (to mix solutions), the 15 possible compounds that are provided, pH strips, distilled water, wooden splints, spatula to get out unknown compound #202, waste bucket, Bunsen burner, graduated cylinder, 500mL beaker for the waste, plastic dishes to measure out compound and the scale.

By using acid-base titration, we determined the suitability of phenolphthalein and methyl red as acid base indicators. We found that the equivalence point of the titration of hydrochloric acid with sodium hydroxide was not within the ph range of phenolphthalein's color range. The titration of acetic acid with sodium hydroxide resulted in an equivalence point out of the range of methyl red. And the titration of ammonia with hydrochloric acid had an equivalence point that was also out of the range of phenolphthalein.. The methyl red indicator and the phenolphthalein indicator were unsuitable because their pH ranges for their color changes did not cover the equivalence points of the trials in which they were used. However, the

In this experiment, the pKa, dissociation constant, of 2-naphthol was determined by measuring the UV-visible absorption spectra of solution of the acid at different pH values.

Dissolved oxygen 3 powder pillow was added to the BOD bottle. Immediately, the stopper was placed back in the BOD bottle, the bottle was inverted for 5 times to mix. As the floc was dissolved a yellow color solution was developed, as an indication of oxygen present. We poured the sample solution from the (60 ml) BOD bottle into a plastic graduate cylinder and adjusted the volume to exact 20 ml. Later on, transferred the solution into a DI rinsed (50 ml) Erlenmeyer flask.

In this lab a acid-base indicator phenolphthalein was used to determine endpoint of a reaction HCl(aq) and KOH(aq). At the end point all of the HCl(aq) would have reacted with KOH(aq), and the pH becomes 7. The phenolphthalein would changed colours from colourless to pink indication when enough KOH(aq) was added. The purpose of numerous trials was to use the average volume of the 3 trials with similar measurements.

There are numerous types of spectrometers that can be utilized for the purpose of this lab; the one utilized for this lab is the Spec20D. An acid-base indicator is a substance that is added to s solution and indicates pH change by means of changing colors. For example, bromocresol green is an acid-base indicator, which is a monoprotic organic acid with a molecular weight of 698.02 g/mol. The absorbance of the indicator solution will be tested over a range of wavelengths utilizing the protonated form to determine the wavelength of highest absorbance; then the same tests will be conducted, but when the indicator is in the deprotonated form. Lastly, the tests will be conducted with both species present, utilizing the wavelengths derived from the first two tests. The data will then be plotted and the pKa can then be derived. For the