Question

A button cell used in watches functions as following
`Zn(s) + Ag _2 O(s) + H_2 O(l)`
`2 A g(s) + Zn^(2+) (aq) = 2 OH^- (aq)`
If half cell potentials are
`Zn^(2+) (aq) +2e^- rarr Zn (s) , E^@ =- 0. 76 V`
`Af_2 O(s) +H_2 O (l) +2e^- rarr`
`2Ag(s) + 2OH^- (aq) , E^@ =0. 34 V`.
The cell potential will be .
A. ` 0.42 V`
B. ` 0. 84 V`
C. ` 1.10 V`
D. ` 1.34 V`

Answer 1

Correct Answer - C
`E_(cell) = E_(OPZ//Zn^(2) ) + E_(PRAg+//Ag)`
`E_(OPZn)^@ + E_(PRAg)^@ + (0.059)/2 log. ([Ag^+]^2)/([Zn^(+2)])`
`=0.76 + 0. 34 + (0.095)/5 log.(0)/([Zn^(2+)])`
`E_(cell)^@ = 1.10 V`.
This is `E_(cell)^@ ` and nor `E_(cell)` since`[ Zn^(2+)]` is not given .