Potentiometry

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Abstract: The purpose of this lab was to use potentiometry to measure the concentration of a specific chemical species in a solution. This was conducted in 2 stages. The first stage involved making a solution of potassium iodide. The potassium iodide was then diluted to several different concentrations that were ran in potentiometer to find the mV of each solution which would then be used to find the PH of the solution. After analyzing a sample of each concentration an unknown solution was compared. Along with the the unknown tap water and deionized water were tested as standards.

Introduction:
A common method for determining the concentration of a solution is a titration. Titrations, however, are not the most efficient method for qualitative analysis because they take a long time and can easily be over titrated and result in the wrong concentration. A more accurate method for determining the concentration of a solution is to use potentiometry. Potentiometry is an electrochemical technique that measures the concentration of a specific species in a solution. This is done my using ion-selective electrodes to measure a potential voltage that is specific to that anion. It is analyzed by comparing the results of unknown solutions to that of a known concentration of the same specific ion. These different readings are then compared using a calibration curve. The calibration curve then determines the concentration of X- in units of molarity. Potentiometry is more favored because it is cheaper, faster, and easier to use than doing simple titrations. The main component of potentiometry is the indicator electrode. When the indicator electrode is immersed in solution containing the specific ion, the potential at the indicator electrode will depend upon the X- ion concentration according to the Nernst equation. It is important to remember before completing an experiment in potentiometry that using instrumental methods initially involves calibration. This is...
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