Question

A fluoride electrode was used to determine the amount of fluoride in drinking water samples. The results given in the table below were obtained for four standards and two unknowns. Constant ionic strength and pH conditions were used.

Solution Containing F-

Potential vs. SCE, mV

5.00 × 10-4 M

0.02

1.00 × 10-4 M

41.4

5.00 3 10-5 M

61.5

1.00 3 10-5 M

100.2

Unknown 1

38.9

Unknown 2

553

(a) Plot a calibration curve of potential versus log[F‑]. Determine whether the electrode system shows Nernstian response.

(b) Determine the concentration of F- in the two unknown samples by a linear least-squares procedure.

Answer 1

fluoride electrode was used to determine the amount of fluoride in drinking water samples. The results given in the table below were obtained for four standards and two unknowns. Constant ionic strength and pH conditions were used.

Solution Containing F-

Potential vs. SCE, mV

5.00 × 10-4 M

0.02

1.00 × 10-4 M

41.4

5.00 3 10-5 M

61.5

1.00 3 10-5 M

100.2

Unknown 1

38.9

Unknown 2

553

(a) Plot a calibration curve of potential versus log[F‑]. Determine whether the electrode system shows Nernstian response.

(b) Determine the concentration of F- in the two unknown samples by a linear least-squares procedure.

Step-by-step explanation:

The data given is used in the following spreadsheet to plot the calibration curve

Calibration curve of electrode potential versus