The metal that reacts steadily with acid to give an orange-brown solution is iron (Fe).

Here's why:

* Reaction: Iron reacts with acids like hydrochloric acid (HCl) or sulfuric acid (H₂SO₄) to produce iron(II) ions (Fe²⁺).

* Solution Color: Iron(II) ions in solution are typically pale green. However, in the presence of air, they readily oxidize to form iron(III) ions (Fe³⁺).

* Orange-Brown Solution: Iron(III) ions in solution are responsible for the characteristic orange-brown color.

Reaction Equation:

Fe(s) + 2HCl(aq) → FeCl₂(aq) + H₂(g)

(Iron reacts with hydrochloric acid to form iron(II) chloride and hydrogen gas)

2FeCl₂(aq) + Cl₂(g) → 2FeCl₃(aq)

(Iron(II) chloride is oxidized by chlorine to form iron(III) chloride)

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