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Electrochem. Lab: Measuring Reduction Potentials & Evaluating Equilibrium Constants - Prof, Lab Reports of Chemistry

A lab experiment in electrochemistry where students measure standard reduction potentials of various metals using a voltage meter and calculate their half-cell potentials using the nernst equation. The lab also includes instructions for evaluating equilibrium constants by measuring the voltage of a silver electrode in a solution of silver ions and hydrochloric acid.

Typology: Lab Reports

Pre 2010

Uploaded on 08/19/2009

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koofers-user-2mx 🇺🇸

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Electrochemistry Lab
Edited 8/20/2008
Equipment and Supplies:
1) Cell Well Plate
2) Filter paper (cut into strips for salt bridges)
3) Metal electrodes, strips of Zn, Cu, Ag, Sn, and Pb
4) ~ 10 mL 0.1 M solution containing the following ions Zn
2+
, Cu
2+
, Ag
+
, Sn
4+
, and Pb
4+
5) ~ 10 mL 0.1 M solution of KNO
3
6) ~ 10 mL 12 M HCL solution
7) Voltage Meter with electrical leads
Procedure:
Measurement of Standard Reduction Potentials
1. In a well plate, pick a well with 8 neighbors around (to be the center one, see picture). In the
center one put your KNO
3
salt solution, in a neighboring one place your metal ion solution
and a strip of the same metal in the well (so CuSO
4
solution with a strip of Cu metal in it).
Each well should have ~ 5 mL of a 0.10 M metal solution in it, record which solution are
located where. You will need two wells that have the silver solution in them, one will
not be used until then next section. Note metal strips may need to be sanded to remove
the oxidation layer.
2. Connect lead with alligator clips to the voltage meter.
3. Take strips of filter paper, wet them with the KNO
3
solution then use them to connect the
various metal ion wells to the center KNO
3
well (see the white strips in the picture). These
strips of paper are acting as salt bridges.
4. Turn on the voltage meter and set it to DC voltage in the millivolt range. Now clip the
alligator clip coming from the positive side of the voltage meter to the silver metal strip.
Clip the other to the copper strip, wait 15 sec and record the voltage. Repeat this with the
other metals always using silver as the positive side. Record the metals and the voltage
value.
5. Using the Nernst equation to correct for the concentration of your solutions and given the
pf3

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Electrochemistry Lab

Edited 8/20/

Equipment and Supplies:

  1. Cell Well Plate
  2. Filter paper (cut into strips for salt bridges)
  3. Metal electrodes, strips of Zn, Cu, Ag, Sn, and Pb
  4. ~ 10 mL 0.1 M solution containing the following ions Zn2+, Cu2+, Ag+, Sn4+, and Pb4+
  5. ~ 10 mL 0.1 M solution of KNO 3
  6. ~ 10 mL 12 M HCL solution
  7. Voltage Meter with electrical leads

Procedure: Measurement of Standard Reduction Potentials

  1. In a well plate, pick a well with 8 neighbors around (to be the center one, see picture). In the center one put your KNO 3 salt solution, in a neighboring one place your metal ion solution and a strip of the same metal in the well (so CuSO 4 solution with a strip of Cu metal in it). Each well should have ~ 5 mL of a 0.10 M metal solution in it, record which solution are located where. You will need two wells that have the silver solution in them, one will not be used until then next section. Note metal strips may need to be sanded to remove the oxidation layer.
  2. Connect lead with alligator clips to the voltage meter.
  3. Take strips of filter paper, wet them with the KNO 3 solution then use them to connect the various metal ion wells to the center KNO 3 well (see the white strips in the picture). These strips of paper are acting as salt bridges.
  4. Turn on the voltage meter and set it to DC voltage in the millivolt range. Now clip the alligator clip coming from the positive side of the voltage meter to the silver metal strip. Clip the other to the copper strip, wait 15 sec and record the voltage. Repeat this with the other metals always using silver as the positive side. Record the metals and the voltage value.
  5. Using the Nernst equation to correct for the concentration of your solutions and given the

half-cell value for Ag+/Ag E^0 values is 0.80 V, calculate the half cell E^0 ’s for the other metals and compare this value to the literature.

Evaluation of Equilibrium Constants

  1. In the extra silver solution well you created before add about 15 drops of 12 M HCl and immerse a freshly sanded piece of silver foil in this solution and measure the voltage against the other silver cell.
  2. Disconnect the voltmeter and wait 1 min, then reconnect and measure again, repeat this process 3 more times for statistical purposes.
  3. Clean up setup and dispose of all heavy metals in appropriate waste containers.

Fill out attached sheet and turn in.

Other K’s that you may be asked to measure.