Introduction In analytical chemistry, there are numerous methods that can be utilized in order to analyze different substances by determining the composition or concentration of a said substance, which is the main goal (Analytical Chemistry, n.d.). One of those methods available, and used widely in analytical chemistry, is spectroscopy. Spectroscopy utilizes the quantification of light; which is based upon intensity, amount absorbed, and amount transmitted, in order to determine the concentration of a given substance (Vo, 2016). For the following lab, the main goal is to determine the pKa of an acid-base indicator by means of spectroscopy. 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
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
In order for the media to show the change in acidity the solutions are modified and include an indicator chemical. This indicator will change color depending on the ph level of the media it is in. For all the media used in this experiment, the indicator changes to a yellow color when in the presence of an acid and turns magenta/pink when in the presence of a base or alkali.
Discussion of Results and Scientific Explanations: The goal of this laboratory was learn how to use the Spectrophotometer to analyze the phosphate content in colas. This is important because the consumers believe that the buffering capacity of phosphate within the colas will settle their upset stomachs. A spectrophotometer, or Spec 20, measures how much a chemical substance absorbs and transmits. The next goal is to determine the relationship between absorbance and transmittance. Transmittance is a measurement of the amount of light that passes through a substance.
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.
19. Stir the solution with a toothpick and observe any changes. Measure the pH of the new solution and record into Table 2.
The preparation for the experiment started by gathering the solutions of enzyme Peroxidase, substrate hydrogen peroxide, the indicator guaiacol and distilled water. Two small spectrometer tubes and three large test tubes with numbered labels. In addition, one test tube rack, one pipet pump and a box of kimwipes were also gathered. Before the experiment, the spectrometer must be set up to use by flipping the power switch to on. Following, the machine was warmed up for 10 minutes and the filter lever was moved to the left. In addition, I set the wavelength to 500 nm with the wavelength control knob. Before the experiment, I had to create the blank solution by pipetting 0.1 ml of guaiacol, 1.0 ml of turnip extract and 8.9 ml water into tube #1. Following the creation of the blank, a control 2% solution was created.
The purpose of this virtual lab is to observe the acid-base balance in the urinary system by how PCO2 and blood pH affect the H+ and HCO3- in the urine. The renal compensation is a mechanism that shows the kidneys manage to change pH in correct way if the respiratory system is not healthy. The kidneys are two organs that help remove wastes and extra fluids out of the body. The acid-base balance is when the blood need to keep the balance of
When handling the Acid or Base to avoid getting any substance in eyes: Use protective eyewear
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.
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
The purpose of this experiment was to determine the pKa of the bromothymol blue (indicator) through absorption spectroscopy. Bromothymol blue being a monoprotic acid base indicator, displays different colors at different pH because of the differences in the ratio of the conjugated acid and base form. The fraction of conjugate acid and base was interpolated for the solutions through the acquired absorbance spectrum of the bromothymol blue at various pH. The rearranged form of Henderson Hasselbalch equation was graphed as a function of pH to determine the pKa of the indicator.
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
Spectrophotometry has various uses in different fields of science. It can be used in obtaining the concentration and the identity of a solution. In order to test
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.