Ise Determination of Fluoride Content in Various Substances

ISE Determination of Fluoride subject in Various Substances CHM 222 A 4 / 20 / 2007 IntroductionThe ion discriminating electrode used was made up of a silver / silver chloride origin electrode and a glass electrode. The pH of the electrochemical cell is determined by monitoring the electrical latent difference between the half-cells. The glass electrode is an ion selective electrode (ISE), which only responds to the hydronium ion concentration / activity in a solution under a large range of conditions.In this experiment, we are measuring the fluoride ion concentration, which operator our electrode responds to fluoride ion concentrations. Procedure And Data Standard Solutions Concentration (M) Potential (mV) 0. 9967 x 10-6 15. 0 0. 9967 x 10-5 1. 4 0. 9967 x 10-4 -42. 0. 9967 x 10-3 -101. 1 0. 9967 x 10-2 -160. 8 0. 9967 x 10-1 -219. 0 Unknown 6 was used for this lab group. It produced a potential difference of -196. 8 mV. This was then used in the equivalence derived from our standard solutions and found to have a F- = 0. 0618 M. Preparation of the toothpaste sample was through with(p) by a sonicator.Then, the electrical potential difference was measured again, serious as in the standard solutions and unknowns. It was found to have a potential of -85. 6 mV. Inserted into the equation, F- = 3. 31 x 10-4 M. CalculationsSee attached sheets. ResultsToothpaste F- = 3. 31 x 10-4 M Unknown 6 F- = 0. 0618 M Label Value in Toothpaste 0. 15% w/v Calculated Value in Toothpaste 0. 8 mg / g 0. 8 mg/g converted to w/v (g/100 mL) is approximately 0. 1144% w/v. In comparison with the label, the figure error is found to be about -24%.A potential ejaculate of error could be found in the method of dissolving the toothpaste. thither were a lot of bubbles formed, thus allowing for greater possibility of misreported volumes of solution. Also, the pH / V meter had difficulty settling on values during the standard measurements, which would metamorphose the regres sion line. The ISAB seemed to work better with stronger concentrations of F-, as the regression line see to it better toward the latter part of the plot. However, the pH region seemed to be less(prenominal) important than the F- concentration.