Match each chemical phenomenon or process involving iron and its compounds listed on the l… — JAMB UTME

Match each chemical phenomenon or process involving iron and its compounds listed on the left with its corresponding chemical principle or characteristic observation on the right.

Galvanizing iron structural beams with a thin coating of zinc metalProvides sacrificial cathodic protection because the coating metal is more electropositive than iron.
Addition of aqueous sodium hydroxide ( $\text{NaOH}$ ) to iron(II) tetraoxosulfate(VI) solutionForms a dirty-green precipitate that turns reddish-brown upon exposure to atmospheric oxygen.
Accumulation of molten slag ( $\text{CaSiO}_3$ ) at the hearth of the blast furnaceFloats on molten iron due to lower density, protecting the metal from re-oxidation by blast gases.
Reaction of aqueous iron(II) ions with acidified potassium tetraoxomanganate(VII)Decolorizes the purple solution as iron(II) is oxidized to iron(III) while manganese(VII) is reduced to manganese(II).

Answer

1. Galvanizing iron structural beams matches with providing sacrificial cathodic protection due to higher electropositivity of zinc.
2. Addition of aqueous sodium hydroxide to iron(II) tetraoxosulfate(VI) matches with forming a dirty-green precipitate that turns reddish-brown in air.
3. Accumulation of molten slag at the blast furnace hearth matches with floating on molten iron to prevent re-oxidation.
4. Reaction of aqueous iron(II) ions with acidified potassium tetraoxomanganate(VII) matches with decolorizing the purple solution via redox reaction.

Each pair correctly connects an iron chemical phenomenon with its true underlying property: zinc sacrificial protection relies on standard electrode potential differences;

\text{Fe}^{2+}

precipitation produces dirty-green

\text{Fe(OH)}_2

that oxidizes to brown

\text{Fe(OH)}_3

; slag (

\text{CaSiO}_3

) protects extracted molten iron from re-oxidation at the furnace base; and

\text{Fe}^{2+}

reduces purple

\text{MnO}_4^-

to colorless

\text{Mn}^{2+}

Step-by-Step Solution

Analyze the principle of rusting prevention via galvanization

Zinc is more reactive (more electropositive) than iron, so it corrodes preferentially in an electrochemically sacrificial manner.

Protective coatings composed of metals above iron in the electrochemical series function sacrificially.

Identify qualitative test reactions for iron(II) ions with strong bases

Adding

\text{OH}^-

ions to

\text{Fe}^{2+}

forms insoluble dirty-green

\text{Fe(OH)}_2

, which oxidizes in air to hydrated iron(III) oxide/hydroxide.

Iron(II) compounds undergo atmospheric oxidation rapidly in alkaline media.

Evaluate the industrial function of slag in the blast furnace hearth

Molten

\text{CaSiO}_3

forms an immiscible layer above liquid iron due to density differences, preventing oxygen in incoming air blasts from re-oxidizing the extracted metal.

Physical separation of hot molten iron from oxidative gases is crucial to preserve yield.

Examine redox properties of iron(II) species with standard oxidizing agents

\text{Fe}^{2+}

is oxidized to

\text{Fe}^{3+}

, while purple

\text{MnO}_4^-

is reduced to colorless

\text{Mn}^{2+}

in acidic solution.

Potassium tetraoxomanganate(VII) is a strong oxidizing agent used to confirm reducing species like

\text{Fe}^{2+}

Key Concept

Chemical reactivity, industrial extractions, qualitative identification, and corrosion mechanisms of iron and its compounds

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