Experiment 9 and 10: Volumetric/Vinegar Analysis
The goal of the experiment that was conducted was to figure out both the molar concentration of NaOH and the standard mole ratio of the NaOH solution. In order to find the concentration of the NaOH solution, volumetric analysis was used. In volumetric analysis, a titration mechanism was utilized in order to find the reaction that the base will end up having with KHC8H4O4., also known as KHP. Phenolphthalein, which is the indicator that was used in this experiment, assisted in figuring out at exactly what point was there neutralization. The indicator turns the solution into a bright pink color once neutralization has occurred. In experiment 10, the average molarity of NaOH that was found in experiment nine was used in order to find out if the vinegar that was being used in the experiment contained around the same percent mass of acetic acid that is found in regular vinegar. The experimental value of NaOH that was used was 1.0425 grams and the molarity of NaOH was found to be 0.089 m/L of NaOH. Towards the conclusion of the experiment, the average percent mass of acetic acid was calculated and found to be 1.695%. Regular house hold vinegar’s average percent mass of acetic acid usually ranges to 4-5%. Based on the percent mass of acetic acid obtained in the experiment, the vinegar that was used in experiment 10 was clearly not house hold vinegar. The hypothesis for this experiment was, if the average percent mass of acetic acid ranged between 4-5%, then it is house hold vinegar. However, due to the results from the experiments conducted, this hypothesis was rejected.
In order to obtain the results that the groups were searching for, titration was used in both experiments to find the answer. The method of titration involves the measurement of KHP and NaOH. Afterwards, the volumetric analysis was used, with the indicator included. The experiment starts by finding the measurements of KHP. The indicator was added later on, and then the titration began with the NaOH solution. It was apparent once the solution was neutralized because the indicator caused the solution to turn bright pink.
The experiment also required the utilization of volumetric mass in order to find the percent mass of acetic acid in vinegar. The mass of vinegar is then titrated along with the indicator endpoint with the sodium hydroxide solution. In order to find the average acetic percent mass of vinegar, the concentration found in NaOH in experiment 9 was utilized together with the known volume of NaOH.
Please refer to Experiment 9 and 10 on pages 127-136 and 137-142, of Laboratory Manual for Principles of General chemistry 9th Edition by J.A. Beran. The only deviation that was performed during this experiment was the two to three extra drops of the indicator phenolphthalein in order to distinguish a titration point.
|Table 1: Measurement |Trial 1 |Trial 2 | |Mass of KHC8H4O4.(g) |.509 g |.501 g | |Buret Reading of NaOH (mL) |28.3 mL |26.7 mL |
Table 1 shows the measurements recorded for experiment 9, volumetric analysis
|Table 2: Calculations |Trial 1 |Trial 2 | |Moles of KHC8H4O4 (mol) |.000303 |.0002485 | |Volume of NaOH Dispensed (L) |.0034 |.0032 | |Molar Concentration of NaOH (mol/L) |.089...
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