Fluoride ion selective electrodes obey the following equation: E(V) = K - (0.059

Question

Fluoride ion selective electrodes obey the following equation:

      E(V) = K - (0.0592)log[F-]

where the fluoride concentration is expressed as mol/L and the temperature coefficient is normally equal to 1.

In a normal calibration procedure you dilute a standard fluoride solution to between 10 and 20 mg/L fluoride ion and then measure the response of the electrode. You then plot the data and do a linear regression to obtain the fitting coefficients K and . Use the plotting and linear regression tools in Excel to calculate K and from the data in the table. The coefficient is close to 1, and can be determined from a calibration curve.

1) What value of K do you obtain from your plot?

2) What value of do you obtain from your plot?

Explanation / Answer

E(V)= K-B*0.0592*log(F-), so a plot of E(v) vs log (F-) gives straight line whose slope is -B*0.0592 and intercept is K. Hence, a plot of E(v) vs log (F-) is generated. The plotted data is shown below

from the plot, slope = -0.056 = -B*0.0592, B= 0.945 and intercept K=-0.290

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