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Colors of Manganese Ions
Recommended Grade Level(s):
Appropriate for: Middle school and High school
Time Requirements:
Activity Time: 20 minutes
Teaching Topics & Concepts:
• Illustrate the various oxidation states of an element
• Balancing redox equations
• Transition metals
• Evidence, models, and explanation
• Constancy, change, and measurement
Background:
The chemical element manganese is classed as a transition metal. Transition metals are known for having more than one stable
oxidation state; manganese has more than any other. It was first recognized as a distinct chemical element in 1740 after chem-
ist Johann H. Pott prepared potassium manganate by fusing caustic potash (potassium hydroxide) with pyrolusite (manganese
dioxide) in the air. The color changes he observed in the product were green/blue/red/green, establishing that pyrolusite did not
contain iron. In this activity, students can demonstrate the oxidative states of manganese and make their own observations.
Materials:
• Potassium permanganate, KMnO4 (0.1 M)
• Sodium hydroxide, NaOH (2.0 M)
• Sulfuric acid, H2SO4 (3.0 M)
• Sodium bisulfite, NaHSO3 (0.1 M)
• EDTA (1.0 M)
• Manganese(ll) sulfate, MnSO4 (powder)
• (5) 100 mL beakers
• 50 mL graduated cylinder
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Safety
• Read the SDS sheets for all chemicals before using them.
• Adult supervision required when handling chemicals.
• Wear safety glasses, gloves, and lab coat.
• Concentrated acids and bases are used.
• Permanganate solution will stain.
• Sulfuric acid, potassium hydroxide, and sodium hydroxide are corrosive to eyes, skin, and other body tissue.
They are also toxic by ingestion. Mixing sulfuric acid with water may cause spattering and severe
heat of dilution.
• Potassium permanganate is a powerful oxidizing agent and a common cause of eye accidents.
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