An investigation into the ability of metals to protect iron from rusting
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Introduction
An investigation into the ability of metals to protect iron from rusting Aim To investigate the ability of metals to act as a sacrificial protector of iron, preventing or reducing rusting. Theory Iron oxide is more stable than iron metal, so when given the opportunity iron will be readily oxidised. Iron reacts with oxygen and water to form a hydrated form of iron(III) oxide (Fe2O3�xH2O), known as rust, which is permeable to air and water so the metal underneath the rust layer continues to corrode1. This diagram shows the reactions which occur in a droplet of water on the surface of a piece of iron or steel: Source 1 The iron atoms readily give away two electrons each, which react with oxygen and water molecules to form hydroxyl ions. These ions reacts with the iron ions to form iron hydroxide, which is then further oxidised and hydrated to give the iron(III) oxide. The higher concentrations of dissolved oxygen at the edges of the drop mean that the reduction reactions happen around the edge, leaving a pit in the metal under the middle of the drop. The rust forms away from the surface of the iron, as the iron and hydroxyl ions diffuse away. ...read more.
Middle
On the other hand, because magnesium and zinc have a more negative electrode potential, they will donate electrons more readily than iron, so the iron will be protected. However, as this experiment will most likely be under non-standard conditions (1atm pressure, 298K), these electrode potential values may vary. The ferroxyl indicator is a solution of ions, which increase the conductivity of the solution compared to distilled water. Also, the ferroxyl indicator is hot when made up, which will increase the temperature of the reaction. Equipment Quantity Equipment Other details 30 Iron nails 0.3g each 6 pieces each Magnesium sheet 0.1g each 1cm x 1cm squares Copper sheet Zinc sheet Lead sheet 36 Test tubes 6 Test tube racks 1 5cm3 graduated pipette For ferroxyl indicator, gradated every 0.1cm3 1 Wheel pipette filler 108cm3, plus extra to wash pipette Fresh ferroxyl indicator Concentration WITHOUT GELATINE PLEASE; YOU SAID IT IS NOT NECESSARY SO WHY WASTE AN ANIMAL'S LIFE?! 2 Colorimeters Make and model 36 Clean plastic cuvettes To fit colorimeter 36 Bulb pipettes To transfer mixture from test tubes to cuvette Fine grade sandpaper To clean metals 1 Balance Reading to 0.01g 1 100cm3 beaker To hold the ferroxyl indicator 6 Stopwatches To 0.01 seconds Method 1. ...read more.
Conclusion
Repeat for the other 5 pieces of magnesium, and place each in a test tube. Start a stopwatch. Label these 6 test tubes with "Fe + Mg". 7. Repeat with the 6 pieces of each of the other metals, and label the test tubes with "Fe + Cu", "Fe + Zn" and "Fe + Pb" as appropriate. Start a stopwatch for each set of 6 test tubes. 8. Set up the colorimeter MORE DETAIL 9. Use the bulb pipette to transfer some of the ferroxyl indicator into a plastic cuvette, to a depth of less than 1cm from the top.. Ensure the cuvette is only held on the frosted sides, as the light is shone through the clear sides and fingerprints could leave a smudge, which will absorb light and therefore create an error in the readings. 10. Place the cuvette in the colorimeter with the blue/green filter, the side with the arrow facing the light source. Close the lid and take a reading for the blue/green absorbance. Repeat in the colorimeter with the red filter and record both readings. 11. Repeat steps 9 and 10 for each of the solutions at 10, 20, 30, 40, 50 and 60 minutes, shaking the test tube first to unify any colour change. Use a different test tube each time. ...read more.
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