# Ion selective electrode problem

The data below is obtained with a potassium ISE. To avoid interferences from H+ and

variations in ionic strength all solutions were made to contain 0.33 M Ca(NO3)2 and

0.0010 M NaOH. An unknown solution was similarly prepared and gave a reading of

-0.0273 volts.

a) What is the slope of the ISE response? (This is the same as the coefficient of the log

term in the ISE equation). What is the value of E', (also known as k)?

b) What is the concentration of K+ in the unknown?

c) What is the lowest [K+] value that can be accurately measured using the ISE and the

procedure described?

d) What is selectivity constant, kK,Na , for the ISE?

Log [K+] E (volts)

-1.3 -0.165

-2.3 -0.221

-3.0 -0.259

-3.7 -0.298

-4.7 -0.350

-5.3 -0.381

-6.3 -0.413

-7.0 -0.421

-8.0 -0.424

-9.0 -0.424

https://brainmass.com/chemistry/oxidation-reduction-and-electrochemistry/ion-selective-electrode-problem-11547

#### Solution Preview

See the attachment. Thanks.

The data below is obtained with a potassium ISE. To avoid interferences from H+ and

variations in ionic strength all solutions were made to contain 0.33 M Ca(NO3)2 and

0.0010 M NaOH. An unknown solution was similarly prepared and gave a reading of

-0.0273 volts.

a) What is the slope of the ISE response? (This is the same as the coefficient of the log

term in the ISE equation). What is the value of E', (also known as k)?

b) What is the concentration of K+ in the unknown?

c) What is the lowest [K+] value that can be accurately measured using the ISE and the

procedure described?

d) What is selectivity constant, kK,Na ...

#### Solution Summary

Ion selective electrode problems are analyzed for potassium ISE. The solution is given in the attachment in 450-500 words including tables.