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The standard oxidation potentials of Zn,...

The standard oxidation potentials of Zn, Cu, Ag and Ni electrodes are `+0.76, -0.34, +0.80 and +0.25V` respectively. Which of the following reaction will provide maximum voltage?

A

`Cu+2Ag^(+)(aq)rarrCu^(2+)(aq)+2Ag`

B

`Zn+2Ag^(+)(aq)rarrZn^(2+)(aq)+2Ag`

C

`H_(2)+Ni^(2+)(aq)rarr2H^(+)(aq)+Ni`

D

`Zn+Cu^(2+)(aq)rarrZn^(2+)(aq)+Cu`

Text Solution

Verified by Experts

The correct Answer is:
B
Standard oxidation potentials of Zn, Cu, Ag and Ni electrode are `+0.76,-0.34,-0.80 and +0.25V` respectively. (Given)
`Zn^(+2)+2e^(-)rarrZn,E_("cell")=-0.76V`
`Cu^(+2)+2e^(-)rarrCu,E_("cell")=+0.34V`
`Ag^(+)+e^(-)rarrAg,E_("cell")=+0.80V`
`Ni^(+2)+2e^(-)rarrNi,E_("cell")=-0.25V`
(a) `Cu+2Ag^(+)(aq)rarrCu^(2+)(aq)+2Ag`
`E_("cell")^(@)=E_("cathode")^(@)-E_("anode")^(@)`
`E_("cell")^(@)=0.80-0.34=0.46V`
(b) `Zn+2Ag^(+)(aq)rarrZn^(2+)(aq)+2Ag`
`E_("cell")^(@)=0.80-(-0.76)=1.56V`
(maximum voltage)
(c ) `H_(2)+Ni^(2+)(aq)rarr2H^(+)(aq)+Ni`
`E_("cell")^(@)=-0.25V`
(d) `Zn+Cu^(2+)(aq)rarrZn^(2+)(aq)+Cu`
`E_("cell")^(@)=0.34-(-0.76)=1.00V`
(e) `Zn+2H^(+)(aq)rarrZn^(2+)(aq)+H_(2)`
`E_("cell")^(@)=0-(0.76V)=0.76V`
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