The reactions are Cu+2 (aq)+2e----->Cu Eo=0.337V (1)
Au+ (aq) e-------------->Au , EO=1.68 V
multiplying with 2 and reversing the reaction gives 2
Au----------> 2Au(s) +
2e-Â Â Â Â Â Â Â Â Â Â Â Â Â
Eo=-1.68V (2)
addition of 1 and 2 gives Cu+2(aq) + 2Au-(s)--------> Cu(s)
Eo= 0.337-0.168 =1.343 V Since
deltaG= -nFE, the reactino is spontaneous
b) The second reaction
becuae Na+ +
e-Â Â Â Â Â Â Â Â Â
---------------> Na (s) EO= =2.714 V
Na (s)------------> Na+
+e-Â Â Â Â Â Â Â Â Â Â Â Â Â
Eo= 2.714 V
multiplying by 2 gives 2Na ---------> 2Na+ + 2e- Eo= 2.714
V
Ni+2 + 2e-Â Â Â Â Â Â Â Â Â
-------------. Ni Eo= -0.25V
when added gives 2Na + Ni+2 ------->2Na+ + Ni Eo= 2.714-0.25=
2.646 V
since deltaG= -nFE is -ve, the reaction is possible.
