‘which reaction would most likely require the use of an inert electrode?

An inert electrode is made up of non reactive metals like Platinum

An inert is electrode is required in one of the half cells or both the cells if there is no solid conducting metal in either half reaction. Or we can say that if in any half reaction neither product nor reactant is in solid phase.

From the given equations it is clear that

a) in first cell we have Cu and Ag in solid phase in either side

b) In second reaction the iron is in aqueous phase on both the side of reactant and product

so for reduction of iron or in cathodic half cell we need inert electrode [which does not participate in reaction]

Hence answer is

c) in third reaction Zn and Sn are in solid phase in either side

d) in fourth reaction Al and Ni are in solid phase in either side

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

10 years is the answer