Lab Report

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INTRODUCTION The main goal of pKa of Methyl red experiment was to find the value of pKa of the methyl red and the indicator by using the spectrophotometry. The indicator is important because it is ... commonly use in the science department to help reached the pH wanted. The first in this experiment to dilute the stock solution with HCl and sodium acetate to find the λA and λB. Then, using Beer law to find the molar absorptivity. To find the [HMR] and [MR-] by using the equation 6 and 7 in the lab manual. The last time was to find the pKa of the methyl red. EXPERIMENTAL We followed the experimental procedure outlined by the OU Physical Chemistry I Laboratory Manual without deviation.1 RESULTS solution pH Absorbance at λA (524.7 nm) Absorbance at λB (435.9 nm) [HMR] (M) [MR-] (M) 1 5.40 0.107 0.259 2x10-5 ± 4x10-7 2x10-4 ± 2x10-2 2 5.28 0.122 0.242 3x10-5 ± 4x10-7 1x10-4 ± 2x10-2 3 4.93 0.239 0.215 6x10-5 ±3x10-7 1x10-4 ± 1x10-2 4 4.64 0.310 0.205 8x10-5 ±3x10-7 1x10-2 ± 1x10-2 5 4.45 0.391 0.190 10x10-5 ± 2x10-7 8x10-5 ± 1x10-2 6 4.32 0.509 0.171 1x10-4 ± 1x10-7 5x10-5 ±7x10-3 7 3.87 0.524 0.138 1x10-4 ± 8x10-8 3x10-5 ± 4x10-3 8 3.21 0.623 0.130 2x10-4 ± 5x10-8 1x10-5 ± 2x10-3 Table 3 – The pH, The absorbance, and the concentration of Methyl Red Solutions By using the Beer’s law, the molar absorptivity methyl red solution in acid wasv3780 ± 350 L/mol cm and the red methyl red at basic solution was 673 ± 126 L/mol cm. The molar absorptivity of the basic solution was 181 ± 4.7 L/mol cm and the molar absorptivity of basic [Show More]

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