Write balanced net ionic equations for the following reactions:
a. Solid zinc is placed in a solution of lead (II) nitrate.
b. Solid nickel is placed in a solution of copper (II) sulfate.
c. A silver nitrate solution is poured over solid tin.
d. Solid iron is immersed in a solution of tin (II) nitrate.

Zn(s)+Pb(NO3)2---> Zn(NO3)2 + Pb
Pb(lead) has higher reduction potential then Zn(zinc) hence Zn will get oxidized and Pb2+ will get reduced.

Ni (s) + CuSO4-----> NiSO4 +Cu 
Cu (copper)has higher reduction potential then Ni (nickel)hence Ni will get oxidized and Cu 2+ will get reduced.

Sn (s) +2 AgNO3-----> Sn(NO3)2 +2Ag
Tin(Sn) has lesser reduction potential then Silver (Ag)hence Sn will get oxidized and Ag+ will get reduced.

Solid iron is immersed in a solution of tin (II) nitrate...No reaction as
Tin(Sn)2+  has lesser reduction potential then Iron2+ hence Sn2+  will remain oxidized  and Fe in  reduced state.