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Answer 1 · 2016-10-18T02:33:25

#MnO_2(s) +3Ag^(+) + 2H_2O(l) rarr MnO_4^(-) + 3Ag(s)darr + 4H^(+)#

Are charge and mass balanced?

#"Oxidation: " Mn(IV) rarr Mn(VII)#

#MnO_2(s) +2H_2O(l) rarr MnO_4^(-) + 4H^(+)+3e^-# #(i)# #;E^@=-1.68V#

#"Reduction: " Mn(IV) rarr Mn(VII)#

#Ag^(+) + e^(-) rarr Ag(s)# #(ii)# #;E^@=0.80V#

#"Overall: "1xx(i)+3xx(ii)#,

#MnO_2(s) +3Ag^(+) + 2H_2O(l) rarr MnO_4^(-) + 3Ag(s)darr + 4H^(+)#
#;E^@=-0.78V#

I looked up the electrode potentials, and the reaction is NOT feasible. Reduction of #Ag^(2+)# would drive the reaction:

#Ag^(2+) + 2e^(-) rarr Ag(s)# #(iii)# #;E^@=1.99V#