Standard Reduction Indicator Electrodes Lab Report

 

Indicator Electrodes

 

  1. A fluoride ion selective electrode is used to measure the amount of fluoride in tap water. To obtain an accurate measurement a calibration is performed by doing a serial dilution of a stock solution of NaF. The original stock solution is 34.56 mM, for the serial dilution a 10.00 mL aliquot of the stock NaF is taken, and diluted to volume with a buffer in a 100.0 mL volumetric flask. This process is repeated five times, with each subsequent aliquot being taken from the new solution that was prepared.


Solution

E (V)

Original Stock

-0.018

Dilution 1

0.042

Dilution 2

0.101

Dilution 3

0.160

Dilution 4

0.219

Dilution 5

0.278

Unknown solution

0.190

 

The unknown is prepared by taking a 25.00 mL aliquot of tap water and diluting it to volume with a buffer in a 100.0 mL volumetric flask.


 

Tabulated are then measurements for the calibration solutions, along with the measurement for the tap water. Determine the ppm

concentration of fluoride in the tap water.


 

 

 

 

 

 

 

  1. A calcium ion selective electrode (ISE) is being developed and tested for the selectivity of the design to calcium. It is known that aluminum and magnesium can interfere with calcium ISEs, from the data collected in the table below, what potential would you expect this ISE to measure when placed in the unknown solution?


 

 

[Ca2+] (mol/)

[Al3+] (mol/)

[Mg2+] (mol/)

Ecell (V)

Solution 1

0.0267

0.0000

0.0000

0.6045

Solution 2

0.0000

0.0500

0.0000

0.6240

Solution 3

0.0500

0.0000

0.0816

0.6187

Solution 4

0.0000

0.0129

0.7820

0.6374

Unknown

0.0135

0.0071

0.2640

?

 

 

  1. A solution containing phosphate is to be analyzed with zinc metal indicator electrode. This electrode uses zinc ions and a zinc cathode along with a Ag/AgCl reference electrode to measure the cell potential. When 15.00 mL of the phosphate solution is mixed with 10.00 mL of 4.50 mM zinc(II) nitrate the cell potential is determined to be -1.043 V. Determine the concentration of phosphate in the original solution. 


 

 

  1. Another zinc metal indicator electrode is used to do a measurement of a cyanide solution. This time the cathode solution is comprised of 10.00 mL of 6.75 mM zinc(II) nitrate. A 20.00 mL solution containing 9.25 mM sodium cyanide is added to the cathode solution. If the anode is still a Ag/AgCl reference electrode, what cell potential will be measured?

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