) Calculate the voltage of the cell you would expect to measure using your Hg standard values. Ni/Ni+2 with Sn/Sn+2. _______________________ V The Standard reduction potential values from Tables (using the Standard Hydrogen Electrode, SHE) are as follows: Sn+2 (aq) + 2 e- ® Sn(s) -0.136 V Ni+2 (aq) + 2 e- ® Ni(s) -0.280 V C) Calculate the voltage of the cell using the standard values from reference tables. Ni/Ni+2 with Sn/Sn+2. _______________________ V
3. Consider that the following half reaction is assigned a half cell voltage of 0.00 V.
Hg+2 (aq) + 2 e- ® Hg (l) Eo = 0.00 V
When this half-cell is paired with each of the following half-cells to form a complete cell in the laboratory, the following cell voltages are measured when the Hg cell is connected to the (+) terminal, thus acting as the cathode.
Hg “Standard” Cell Potentials
Ni/Ni+2 with Hg/Hg+2. 1.134 V
Sn/Sn+2 with Hg/Hg+2. 0.99 V
A) Calculate the reduction potentials using this Hg standard cell.
Ni+2 (aq) + 2 e- ® Ni(s) ________________________ V (Hg Standard)
Sn+2 (aq) + 2 e- ® Sn(s) ________________________ V (Hg Standard)
Mixed Cell Potentials
Now consider combining the Ni/Ni+2 and Sn/Sn+2 half cells to produce a complete cell.
B) Calculate the voltage of the cell you would expect to measure using your Hg standard values.
Ni/Ni+2 with Sn/Sn+2. _______________________ V
The Standard reduction potential values from Tables (using the Standard Hydrogen Electrode, SHE) are as follows:
Sn+2 (aq) + 2 e- ® Sn(s) -0.136 V
Ni+2 (aq) + 2 e- ® Ni(s) -0.280 V
C) Calculate the voltage of the cell using the standard values from reference tables.
Ni/Ni+2 with Sn/Sn+2. _______________________ V
D) When the Sn+2/Sn half-cell is paired with Cd+2/Cd, a cell potential of 0.267 V is measured. In addition, tin metal is seen to precipitate out of solution.
Calculate the reduction potential of Cd+2 (aq) + 2 e- ® Cd(s) under the Hg standard and from the SHE standard.
Cd+2 (aq) + 2 e- ® Cd(s) ________________________ V (Hg Standard)
Cd+2 (aq) + 2 e- ® Cd(s) ________________________ V (SHE Standard)
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