Bromothymol Blue Lab Report

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

The makeup of a compound drastically changes its intermolecular forces (IMFs) with the polar silica gel of a TLC plate; this concept is responsible for the variability of Rf values observed throughout the course of lab. The weaker the IMFs, the further a compound will travel through the silica. For instance, ionic interactions are the strongest IMF, but were not present during this experiment. H-bonding IMFs had the greatest impact for our specific compounds. Resorcinol and 3-chlorobenzoic acid exhibited low Rf values, due to its ability to H-Bond to silica’s hydrogen donors and oxygens acceptors (See graph 1). Both were adept to strongly H-bonded to silica because the compounds contained at least 1 H-donor and 2 H-acceptors. Thus, stronger/more

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 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 purposes of this experiment were to model a bimolecular nucleophilic substitution reaction between potassium hydroxide (KOH) with 1-bromopropane and determine whether it follows a second-order rate law mechanism. A rate constant of 0.0684 M-1 min-1 was obtained for this reaction at 45.1°C, which was determined through equilibrating the reaction and performing titrations of 0.390 M KOH with 0.1000 M hydrochloric acid (HCl). The activation energy calculated from class data was 50.188 kJ/mol, which deviated largely from the literature range value of 72.80–83.76 kJ/mol. It was concluded that the reaction was consistent with the predicted SN2 mechanism, based on the regression of a trendline.

C.|NH3 + BTB|A4|The mixture is a lighter royal blue under white paper and a darker royal blue under black paper. The mustard yellow would be an acidic indicator and the royal blue a basic indicator. |

Beer’s Law is a direct liner relationship between the absorbance of light are a selected wavelength and the concentration the absorbing species in the solution. (Sullivan 241). Beer’s Law shows a relationship between several concentrations. To determine if the determine our data consistent with Beer’s law, we will plot a graph of absorbance versus concentration with a linear regression

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 highly conjugated system of the cyanine dyes makes it a very good compound in the development of more efficient solar cells. In this experiment, the maximum wavelength was measured for nine dyes using a UV-Vis spectrum. The result that were obtained agreed with Kuhn’s model for the less polarizable end groups such as 3,3 '-diethyloxadicarbocyanine and 3,3 '-diethyloxatricarbocyanine. That suggested that these two compounds were not as easy to polarize compared to the rest of the dyes. The rest of the dyes required the use of the empirical parameter α to provide more reliable predictions of the wavelengths. This was due to the highly polarized ends of the dyes which needed the adjustment of the parameter to get more accurate results. The series with the higher polarizable end groups’ absorbed higher wavelength light than the less polarized groups. This supported the idea of the one-dimensional box. Also, higher wavelength was determined to be associated with longer conjugated carbon methine chains between the Nitrogen atoms. Kuhn’s free electron model was very reliable for this system.

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.

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.

Purpose/Hypothesis: The purpose of this experiment is to use both cabbage juice and pH paper to determine the pH of household items. This way, we can tell which products are basic and which one are acidic. If we use cabbage juice as an universal pH indicator by comparing it to pH paper then pH determined by the cabbage juice will be unstable because by using cabbage juice, it can be different depending on how diluted it is.

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.

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.