Fluoride ion selective electrodes obey the following equation: E(V) K B(0.0592)l

Question

Fluoride ion selective electrodes obey the following equation: E(V) K B(0.0592)log[FT] where the fluoride concentration is expressed as mol/L and the temperature coefficient B 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 B. Use the plotting and linear regression tools in Excel to calculate K and B from the data in the table. The coefficient B is close to 1, and can be determined from a calibration curve. F concentration E(V) (mg/L) 10.0 -0.295 0.299 12.0 -0.303 14.0 0.307 16.0 18.0 0.310 0.312 20.0 What value of K do you obtain from your plot? 402 -0.2364 What value of B do you obtain from your plot? 40M 0.9848

Explanation / Answer

First you need to pass all of the values of F from mg/L to mol/L. All you have to do is use the atomic weight and the formula: mol = m/Am. So in doing this, the values are: Atomic weight of F = 19 g/mol

Now, let's calculate the value of -0.0592*logF. And those values, along with the E, are the ones we re going to use to calculate K and Beta. The next chart shows the results for both of the cases:

Now with this value, I'll put this on excel and the results are the following:

For the first case:

K = -0.4862

B = 0.9865

For the second case:

K = -0.5204

B = 0.9514

Those should be the values of K and B. the r2 is close to 1 too so it should be correct both of them.

mg/L 10 12 14 16 18 20 mol/L 0.526x10-3 0.632x10-3 0.737x10-3 0.842x10-3 0.947x10-3 1.053x10-3

Related Questions

Navigate

• Browse (All)
• Browse F
• Subjects

---