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In the button cell, widely used in watch...

In the button cell, widely used in watches, the following reaction takes place
`Zn(s)+Ag_(2)O(s)+H_(2)O to Zn^(2+)(aq)+2Ag(s)+2OH^(-)(aq)`
Determine `E^(@)` and `DeltaG^(@)` for the reaction.
(Given : `E_(Ag^(+)//Ag)^(@)=+0.80 V,E_(Zn^(2+)//Zn)^(@)=-0.76 V`

Text Solution

Verified by Experts

The cell reaction in button cell:
`Zn__(s) + Ag_(2)O_(s) +H_(2)O_(1) rightarrow Zn_(aq)^(2+) + 2Ag_(s) + 2OH^(-)(aq)`
(i) Calculation of `E_((cell))^(@)`
Reaction : `ZN_((s)) rightarrow Zn_((aq))^(2+) + 2e^(-)`
Cathode: `Ag_(2)O _((s)) + H_(2)O _(1) + 2e^(-) to 2Ag_((s)) + 2OH_((aq))^(-) + 2e^(-)+ 2e^(-)`
n= 2
`E_(cell)^(@)= E_("cathode") ^(@)- E_("anode")^(@) = E_(Ag_(2)O //Ag)^(@) - E_(Zn^(2+//Zn)) = 0.80 - (- 0.76)V 1.56V`
(ii) Calculate of `Delta _(r) G^(@)`
`Delta_(r) G^(@) = -nEF_(cell)^(@)`
`= -2xx96500 Cmol^(-1) xx1.56V = - 301080 C V m ol^(-1) = - 301 KJmol^(-1)`
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