Okay, let's evaluate the options to determine which half-cell will result in a positive cell potential when combined with the Cu2+/Cu half-cell:
1. Fe2+/Fe3+: This half-cell converts Fe2+ ions to Fe3+ ions. The standard cell potential for Fe2+/Fe3+ is +0.77 V. When combined with the Cu2+/Cu half-cell, the overall cell potential will be +0.77 V - E°Cu2+/Cu = +0.77 V - 0.34 V = +0.43 V. This is a positive value, so Fe2+/Fe3+ will work.
2. Ag/Ag+: The standard cell potential for Ag/Ag+ is +0.80 V. Combined with Cu2+/Cu, the cell potential would be +0.80 V - 0.34 V = +0.46 V. This is also positive, so Ag/Ag+ can be used.
3. Sn2+/Sn: The standard cell potential for Sn2+/Sn is -0.14 V. Combined with Cu2+/Cu, the cell potential would be -0.14 V - 0.34 V = -0.48 V. This is negative, so Sn2+/Sn will not result in a positive cell potential.
In summary, the half-cells that will work with Cu2+/Cu to give a positive overall cell potential are:
1. Fe2+/Fe3+
2. Ag/Ag+
Sn2+/Sn will give a negative potential and cannot be used.
Does this make sense? Let me know if you have any other questions!