[defencegrid]

I looking at the following two reactions involving iron:


Why is a more concentrated HCl required for Iron III Oxide?

The only thing I can think of is that more Cl- are required from HCl to accommodate Fe3+

[AWK]

Why is a more concentrated HCl required for Iron III Oxide?

[Vidya]

Why is a more concentrated HCl required for Iron III Oxide?

Compare reactivity of Iron (III) oxide with Iron(II) oxide.

[defencegrid]

Why is a more concentrated HCl required for Iron III Oxide?

Compare reactivity of Iron (III) oxide with Iron(II) oxide.

Iron (II) is more reactive than iron III, so it takes a stronger HCl to form Iron (III) Oxide?

[AWK]

Iron (II) is more reactive than iron III, so it takes a stronger HCl to form Iron (III) Oxide?

In your first post you asked about dissolution of oxides.

Both oxides react with solution of HCl. The only problem is the rate of dissolution. Since FeCl₃ can form a complex ion [FeCl₄]^- that depends on concentration of Cl^- hence Fe₂O₃ reacts with more concentrated HCl faster compared to lower concentration solution of acid (this is called a driving force).
Moreover, Fe₂O₃ forms different polymorphs. I expect that their dissolution in HCl will be with different rate.

In my firts post I pointed out that your question is far from precision. Moreover, you trial answer was based on stoichiometry of reactions only.

The extreme case for polymorphs - SiO₂ - quartz reacts easily with HF  (all textbooks inform about this reaction) when its high pressure polymorph - stishovite does not react at all.