Question 1
A solution of MnO42– is electrolytically reduced to Mn3+. A current of 5.29 amp is passed through the solution for 15.0 minutes. What is the number of moles of Mn3+ produced in this process? (1 faraday = 96,485 coulombs)
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0.0493 mol◦
0.148 mol◦
2.74 × 10–4 mol
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0.0164 mol◦
1.10 × 10–3 mol
Question 2
A strip of copper is placed in a 1 M solution of copper nitrate and a strip of silver is placed in a 1 M solution of silver nitrate. The two metal strips are connected to a voltmeter by wires and a salt bridge connects the solutions. The following standard reduction potentials apply:
| Ag +( aq) + e – Ag( s) | E° = +0.80 V |
| Cu 2+( aq) + 2e – Cu( s) | E° = +0.34 V |
Which of the following statements is false?
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Electrons flow in the external circuit from the copper electrode to the silver electrode.◦
The silver electrode increases in mass as the cell operates.◦
There is a net general movement of silver ions through the salt bridge to the copper half-cell.◦
Negative ions pass through the salt bridge from the silver half-cell to the copper half-cell.◦
Some positive copper ions pass through the salt bridge from the copper half-cell to the silver half-cell.
Big Mac and Copper
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