Can anyone one help me solving these pre lab questions. I would really be thankf

Question

Can anyone one help me solving these pre lab questions. I would really be thankful + rate this lab is about (Ion-selective electrode)

The electrode tip is a thin polymer membrane formed on the end of a short piece of tygon tubing. It is fragile. Please handle it carefully. DO NOT remove the tygon tip from the electrode. Do not touch the membrane or allow it to come n contact with anything, especially a stir bar spinning in the bottom of a beaker B. Ionic Strength Adjustor Potentiometric measurements depend on the conductivity of the solution being mea To obtain reliable measurements, the conductivity of all solutions being measured sho be the same. This is achieved by the use of an ionic strength adjustor, a solution that is added to every sample. The solution best suited to use as an ionic strength adjustor will be different for each kind of electrode. Table 9-1 lists some recommended solutions. 2 of sample is the recommended amount to use. sured. uld mL per 100 mL Table 9-1. Recommended ionic strength adjustor solutions. ISA 1 M NH,CI 2 M KCI 5 M NaNO lon Sodium Calcium Chloride Nitrate2 M (NH,)SO C. Making Standard Solutions Calibration of an ion-selective electrode requires a series of solutions containing the spe- cific ion in known concentrations. The easiest way to make a series of solutions of known concentrations is to prepare a stock solution and then perform a serial dilution. When de ciding what solutions to make, keep the following in mind. . The concentrations of your standard solutions should bracket the manufacturer's stated range for the electrode. Because you will need to convert your concentrations into logs, it is best if the standard solutions have concentrations of the form 1.00 X 10 M, where x will vary from 0 to -7. Determining the linearity of the calibration plot is crucial for proper evaluation of its reliability. A minimum of four standard solutions should be employed. To compensate for ionic strength effects, an ionic strength adjustor solution should be added to every sample. There is a different solution for each electrode and they are provided by the prep room. 2 mL per 100 mL of sample is recommended. .

Explanation / Answer

1. Chloride solution is used as a standard solution fo this experiment . The stock solution can be prepared by dissolving 0.1649 g of sodium - chloride in reagent water and dilute to 100 mL in a volumetric flask. Store in a clean bottle.

2. 5M NaNO3 is used as a ionic strenth adjuster.It is prepared by dissolving 42.5 g of sodium nitrate in sufficient reagent water to make 100 mL of solution.

3. We can determine that the electrode is working properly or not by Preparing a calibration curve by plotting measured potential (mV) as a function of the logarithm of chloride concentration. The slope must be 54-60 mV per decade of chloride concentration. If the slope is not acceptable, the ISE may not be working properly.

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