Pencil lead reduction

Iron (III) oxide can be reduced to iron by using a pencil lead.

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Experimental set-up

In the experiment a pencil lead was supported on a white tile and connected at a 12 volt power pack.

A mixture of iron (III) oxide and powdered carbon was placed on top of the pencil lead. A bar magnet was passed over the top of the powdered mixture and none of the solid was attracted to it.

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Chemicals and equipment

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Placing the reaction mixture on a ceramic tile

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Nothing picked up by a bar magnet

The power pack was turned on and the pencil lead glowed brightly. After about a minute and a half of heating the pencil lead broke.

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Thermal reduction

On cooling, when a magnet was passed over the powdered reaction mixture several specks of solid containing iron were attracted to it.

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Attractive product – we’ve made some iron!

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Specks of solid stick to the magnet

A movie of the experiment can be viewed here.

Answers to the questions at the end of last months blog:

  1. Chlorine gas was produced at the anode. The chlorine gas diffused across the tile reacting with the blue litmus paper, the potassium iodide solution and the potassium bromide solution.
  2. Copper metal was produced at the cathode.
  3. Chlorine gas dissolved in water on the surface of the paper. The products of the reaction of chlorine with water were hydrochloric acid which turned the litmus pink and hydrogen hypochlorite which bleached it white.
  4. The potassium iodide turned orange/brown due to the formation of iodine. Chlorine displaced the iodide ions from solution producing chloride ions and iodine.
  5. The potassium bromide turned yellow/orange due to the formation of bromine. Chlorine displaced bromide ions from solution producing chloride ions and bromine.
  6. The blue colour of the copper (II) chloride solution faded as copper metal was deposited at the cathode. The blue colour was due to the copper (II) ions which were removed from solution as they reacted at the cathode.