What is the value of K? Please show work! F - concentration (mg/L) E(V) 10.0 -0.

ID: 933828 • Letter: W

Question

What is the value of K?

Please show work!

F- concentration (mg/L) E(V) 10.0 -0.333 12.0 -0.338 14.0 -0.342 16.0 -0.346 18.0 -0.349 20.0 -0.352 Fluoride ion selective electrodes obey the following equation: E(V) = K - beta is close to 1, and can be determined from a calibration curve. F- concentration (mg/L) E(V) 10.0 -0.333 12.0 -0.338 14.0 -0.342 16.0 -0.346 18.0 -0.349 20.0 -0.352 What is the value of K? Please show work! beta from the data in the table. The coefficient beta . Use the plotting and linear regression tools in Excel to calculate K and beta 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 beta (0.0592)log[F-] where the fluoride concentration is expressed as mol/L and the temperature coefficient

Explanation / Answer

F Molar mass = 19 g/mol

Excel: insert E and conc. in columns A and B

Column C: c(mol/L) = c/19 / 1000)

Column D: log c (M)

Column E: pF = -log c

E (mV)

c (mg/L)

c (mol/L)

(-log c)

-0.333

10.0

0.000526

3.28

-0.338

12.0

0.000632

3.20

-0.342

14.0

0.000737

3.13

-0.346

16.0

0.000842

3.07

-0.349

18.0

0.000947

3.02

-0.352

20.0

0.001053

2.98

Molar mass F =

SLOPE

0.06309

INTERCEPT

-0.539825

beta

1.065708

Insert Chart XY ( E and log c) . The graph reprezent the equation E = K + S log c, where K is INTERCEPT and S is SLOPE. (SLOPE and INTERCEPT are in Excel, Statistical Function)

beta = SLOPE/0.0592

K= INTERCEPT = standard potential