The standard reduction potentials of `Zn^(2+)//Zn,Cu^(2+)//Cu and Ag^(+)//Ag` are respectively -0.78, 0.34 and 0.8 V. The following cells were constructed:
(1) ` Zn |Zn^(2+)|| Cu^(2+)|Cu`
(2) ` Zn |Zn^(2+)|| Ag^(+)|Ag`
(3) ` Cu |Cu^(2+)|| Ag^(+)|Ag `
What is the correct order of of these cells?

Options

A. `2 gt 3 gt 1`
B. `2 gt 1 gt 3`
C. `1 gt 2 gt 3`
D. `3 gt 1 gt 2`

Answer

B

Explanation

`E_((Zn^(2+))//(Zn))^@ = -0.78, E_((Cu^(2+))//(Cu))^@ =0.34, E_((Ag^(+))//(Ag))=0.8`
`E^@` of the cell 1 `= E_((Cu^(2+))//(Cu))^@ - E_((Zn^(2+))//(Zn))=0.34-(-0.78)=1.12V`
`E^@` of the cell 2 `= E_((Ag^(+))//(Ag))^@ - E_((Zn^(2+))//(Zn))=0.8-(-0.78)=+1.58V`
`E^@` of the cell 3 `= E_((Ag^(+))//(Ag))^@ - E_((Cu^(2+))//(Cu))=0.8-0.34=+0.46V`
`therefore` order of `E^@` cell of three cells is, `2 gt 1 gt 3`.