Answer Happy

Please help. All solutions are the same when looking at similar
questions on answers but it is not understandable. Please help me
understand how to get to the answer!
1 consider the following electrode-solution interfaces, and
write the equation for the electrode
reaction that occurs when the potential moved in a negative
direction from a potential where
there is no electrode reaction (such a potential is also called
open-circuit potential)
Pt/Cu2+, Cd2+
Hg/Cd2+, Zn2+
2. Consider the following electrode-solution interfaces, and
write the equation for the electrode
reaction that occurs when the potential moved in a positive
direction from the open-circuit
potential, what is the open-circuit potential range?
Au/Sn2+, I-, Fe2+,