Acid Dissociation Constant of Methyl Red Binghamton University - CHEM 108CHEM 108- C65 Lab #5

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Acid Dissociation Constant of Methyl Red: Laboratory Exercise #5 Introduction Indicators are constantly utilized to discover the amount of a substance located in a solution, or aid in determining i... f there is a presence of a substance within the solution. Weak acids and bases are an example of indicators that are utilized as acid-base indicators. In the equation, HIN+H​2​O <--> H​3​O​+​ + IN​-​, the HIN is the indicator for the acidic solution, and IN​-​ is the indicator for the basic solution; both of these solutions are colored differently. When the concentration ratio of IN​-​ to HIN is at a concentration greater than 100, the color of IN​-​ will be seen, but when the concentration ratio is less than 0.0100, the color of HIN will be seen. Methyl red will be utilized in this experiment as its acid form in order to help discover the ratio. In order to solve for pKa consists of measuring the (MR​-​)/(HMR) ratio of methyl red since there are two forms. Beer’s Law states the absorbing light at a specific wavelength is proportional to its concentration, which means the (MR​-​)/(HMR) ratio can be discovered. To determine the pH of these substances, a pH sensor should be used since HMR and MR​-​ have colored concentrations, which means one can determine their pH visually. The hypothesis of this experiment is that if proper techniques and practices are upheld, that are required for good laboratory results, then the Ka values for the solutions will be discovered, the values for MR​-​ and HMR for each solution will be determined, the pKa values of each solution will be discovered with the equilibrium constant, and the Ka for the methyl red solution will be discovered. The techniques consist of learning how to utilize a pH sensor, preparing a Beer’s Law plot and utilizing it to solve for the(MR​-​)/(HMR) ratio, being careful with NaOAc and HOAc acids (but they are weak, so they aren’t that harmful), properly using the spectrometer and reading it correctly, to properly use all equations, and ensuring that glassware is properly used to obtain accurate volumetric measurements. With the utilization of these useful experimental practices and techniques, good results will result and be portrayed in the data received. The objectives utilized throughout this experiment were to properly perform and operate a spectrophotometer, to discover the ratio of the equilibrium reaction, to determine the values of MR​-​ and HMR for the solutions, determining the pH values at the specific wavelengths received for the solutions made, performing calculations to received the pKa values of the solutions, to determine the (MR​-​)/(HMR) ratios through a pH sensor for the solutions, to learn how to utilize a pH sensor for future laboratory experiments and the current one, to utilize Beer’s Law plots to aid in determining the equilibrium constants of the solutions and the slope of each set, and to properly perform correct procedures and laboratory techniques​1​.​ ​The mathematical equations that follow apply to the laboratory report by providing the average of the Ka (1/mol*L) values along with the standard deviation of them, giving the percent error of the actual Ka (1/mol*L) value of methyl red with the Ka (1/mol*L) value of methyl red received, provides how the MR​-​ and HMR concentration values will be received, and how one can discover the Ka (1/mol*L) values from the pKa values received from the ratio of the concentration of MR​-​ and HMR. The mathematical equations needed to complete and conduct this experiment are as follows: [Show More]

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