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NCERT Class XII Chemistry
Chapter - Electrochemistry
Questions with Solutions

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Question : 6
Total: 32
In the button cells widely used in watches and other devices the following reaction takes place :
Zn(s)+Ag2O(s)+H2O(l)→Zn2+(aq)+2Ag(s)+2OH–(aq)
Determine ΔrG° and E° for the reaction.
Given : E°Ag2O∕Ag=0.344V,E°Zn2+∕Zn=–0.76V,
Solution:  
Zn is oxidised and Ag2O is reduced (as Ag+ions change into Ag)
E°cell=E°Ag2O∕Ag−E°Zn2+∕Zn
=0.344−(−0.76)=1.104V
ΔrG°=−nFE°cell
=−2×96500×1.104
=−2.13×105J
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