Question

Using the standard electrode potentials given below ,predict if the reaction between the following is feasible:
(a) Fe3+(aq) and I- (aq)
(b) Ag+ (aq) and Cu(s)
(c) Fe3+ (aq) and Cu(s)
(d) Ag(s) and Fe3+(aq)
(e) Br2(aq) and Fe2+(aq)

Answer 1

(a) The possible reaction between Fe3+(aq) and I−(aq) can be expressed as,
2Fe3+(aq)+2I−$\rightarrow$2Fe2+(aq)+I2( s)
oxidation Half-equation: 2I−$\rightarrow$+I2( s)+2e−;E0=−0.54
reduction Half-equation :[Fe3+(aq)+e−$\rightarrow$Fe2+(aq)]×2;E0=+0.77 V
2Fe3+(aq)+2I$\rightarrow$2Fe2+(aq)+I2( s);E0=+0.23 V
E0 for the overall reaction is positive. Thus, the reaction between Fe3+ and I(aq)− is possible.

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(b) The possible reaction between Ag+(aq) and Cu(s) can be described as follows:
2Ag+(aq)+Cu(s)$\rightarrow$2Ag(s)+Cu2+
oxidation Half-equation : Cu(s)$\rightarrow$Cu2+(a) +2e−;E0=−0.34 V
reduction Half-equation :[Ag+(aq)$\rightarrow$e−Ag(s)]×2;E0=+0.80 V
2Ag+(aq)+Cu(s)→2Ag(s)+Cu2+;E0=+0.46 V
E0 is positive for the overall reaction is positive. Hence, the reaction between Ag+(aq) and Cu(s) is possible.

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(c) The possible reaction between Fe3+(aq) and Cu(s) is given by:
2Fe3+(aq)+CaV→Fe2+(s)+Cu2+(2q)
oxidation Half-equation :Cu(s)→Cu2+(aq) +2e−;E0=−0.34 V
reduction Half-equation :[Fe3+(aq)+e−→Fe2+(s)]×2;E0=+0.77 V
2Fe3+(aq)+Cu(s)→Fe2+(s)+Cu2+(aq);E0=+0.43 V
E0 is positive for the overall reaction is positive. Hence, the reaction between Fe3+(aq) and Cu(s) is possible

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(d) The possible reaction between Ag(s) andFe3+(aq) is given by:
Ag(s)+2Fe(aq)→Ag+(aq)+Fe2+(aq)
oxidation Half-equation :Ag(s)+→Ag+(aq )+e−;E0=−0.80 V
reduction Half-equation :[Fe3+(aq)+e−→Fe2+(s)]×2;E0=+0.77 V
Ag(s)+2Fe3+(aq)→Ag+(aq)+Fe2+(aq);E0=−0.03 V
Here, E0 for the overall reaction is negative. Hence, the reaction between Ag(s) and Fe3+(aq) is not possible.

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(e) The possible reaction between Br2(aq) and Fe2+( aq ) is given by:
Br2( s)+2Fe2+(aq)→2Br−(aq)+2Fe+3(aq)
oxidation Half-equation :[Fe2+(aq)→Fe+3(aq)+e−]×2;E0=−0.77 V
reduction Half-equation :Br2(aq)+2e−→Br−(aq);E0=+1.09 V
Br2(aq)+2Fe2+(aq)→2Br−(aq)+2Fe3+(aq);E0=+0.32 V
Here, E0 for the overall reaction is positive. Hence, the reaction between Br2(aq) and Fe2+( aq )is feasible.