What is the overall voltage for a redox reaction with the half-reactions [tex]$Ag^{+} + e^{-} \rightarrow Ag(s)[tex]$[/tex] and [tex]$[/tex]Cu(s) \rightarrow Cu^{2+} + 2e^{-}$[/tex]?

A. [tex](-0.34) - 0.80[/tex]
B. [tex]0.34 - 0.80[/tex]
C. [tex]0.80 - 0.34[/tex]
D. [tex]0.80 + 0.34[/tex]



Answer :

To determine the overall voltage for the given redox reaction, we need to consider the standard reduction potentials for each half-reaction.

The half-reactions are:
1. \(Ag^{+} + e^{-} \rightarrow Ag(s)\)
2. \(Cu(s) \rightarrow Cu^{2+} + 2e^{-}\)

The standard reduction potential for the silver reaction is:
[tex]\[ E^{\circ}_{Ag^{+}/Ag} = +0.80 \, \text{V} \][/tex]

The standard reduction potential for the copper reaction is given for the reduction process \(Cu^{2+} + 2e^{-} \rightarrow Cu(s)\), which is:
[tex]\[ E^{\circ}_{Cu^{2+}/Cu} = +0.34 \, \text{V} \][/tex]

However, the copper reaction we are dealing with is the oxidation process \(Cu(s) \rightarrow Cu^{2+} + 2e^{-}\), and we must take the opposite sign for this reaction:
[tex]\[ E^{\circ}_{Cu/Cu^{2+}} = -0.34 \, \text{V} \][/tex]

To find the overall cell voltage, we need to subtract the anode potential (oxidation potential) from the cathode potential (reduction potential). The half-reaction with the more positive reduction potential serves as the cathode. Therefore:

- The cathode reaction (reduction) is \(Ag^{+} + e^{-} \rightarrow Ag(s)\) with \( E^{\circ}_{\text{cathode}} = +0.80 \, \text{V} \).
- The anode reaction (oxidation) is \(Cu(s) \rightarrow Cu^{2+} + 2e^{-}\) with \( E^{\circ}_{\text{anode}} = -0.34 \, \text{V} \).

The overall cell voltage is given by:
[tex]\[ E_{\text{cell}} = E^{\circ}_{\text{cathode}} - E^{\circ}_{\text{anode}} \][/tex]
[tex]\[ E_{\text{cell}} = +0.80 \, \text{V} - (-0.34 \, \text{V}) \][/tex]
[tex]\[ E_{\text{cell}} = +0.80 \, \text{V} + 0.34 \, \text{V} \][/tex]
[tex]\[ E_{\text{cell}} = 1.14 \, \text{V} \][/tex]

Thus, the overall voltage for the redox reaction is 1.14 V, and the correct answer is:
[tex]\[ C. \, 0.80 - (-0.34) \][/tex]

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