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Ward's World Colors of Manganese Activity

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Page 2 Procedure: 1. Pour 50 mL of 0.1 M potassium permanganate in five 100 mL beakers (labeled 1 to 5). 2. To beaker number 1 add 15 mL of 3.0 M sulfuric acid and then, while stirring slowly, add 0.1 M sodium bisulfite until a color change takes place. 3. To beaker number 2 add 20 mL of 2.0 M sodium hydroxide and then, while stirring slowly, add 0.1 M sodium bisulfite until a color change takes place. 4. To beaker number 3 slowly add 0.1 M sodium bisulfite while stirring until a color change takes place. 5. To beaker number 4 add 5 mL of 1.0 M EDTA and a pinch of solid manganese(ll) sulfate; then stir. Expected Results: This activity demonstrates the chemical process of oxidation and reduction or a redox reaction. The color changes we observe are attributed to different oxidation states of manganese as its reduced. Follow up/Extension: • Students can be asked to write balanced equations for beakers 1, 2, and 3 if they are told the oxidation half-reaction is HSO3-1 => SO4-2 • The reduction half-reaction is MnO4-1 => Mn ? where the ? refers to the oxidation state of manganese in the appropriate beaker. • What are the properties of transition metals? • Name the other transition metals besides manganese. How are they different? • Discuss how the burning of fuels, corrosion of metals, and the processes of photosynthesis and cellular respiration involve oxidation and reduction. Teaching notes: • You'll get the most dramatic effect if you swirl the mixture together to combine the reactants thoroughly. • The chart below outlines color corresponding to the various oxidation states of manganese • Advanced students should recognize that H+ or OH– ions influence the identity of the product. They should also be able to write the equations for the reactions. Disposal/Clean-Up: Remaining contents can be placed in the science department's heavy metal waste container for proper disposal. Colors of Manganese Ions (continued) + ward ' s science 5100 West Henrietta Road • PO Box 92912 • Rochester, New York 14692-9012 • p: 800 962-2660 • wardsci.com Find materials for this activity at wardsci.com. Discover more free activities at wardsworld.com Beaker Oxidation State of Mn Color 1 +2 colorless 2 +6 green 3 +4 brown 4 +3 violet/rose 5 +7 purple

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