Investigating the causes of Corrosion to Iron.
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Investigating the causes of Corrosion to Iron Hypothesis I believe that iron needs both oxygen and water in order to form iron oxide (rust). I also believe that iron oxide formation will not occur when neither oxygen nor water is present (test tube numbers 2, 3, 5, and 8). Certain factors can affect the reaction rate: limiting reactants i.e. the amount of water, oxygen and iron present and higher temperatures cause a faster reaction rate. Other reactants may change the reaction completely or alter the reaction rate. In order to test this I added magnesium and salt. Different concentrations of these reactants (diluted and saturated) should also change the reaction rate. Iron can be coated by a more reactive metal i.e. zinc. This is called galvanization. The zinc is higher up in the reactivity series which causes the oxygen and water to react with the zinc. This is called sacrificial protection because the zinc sacrifices itself to protect the iron. Zinc is often used to protect iron. The formula for this reaction is: Oxygen + Iron + Water ? Iron Oxide O2 + 2Fe + H2O ?
from both the oxygen and the water by reacting with them instead. 6 Galvanized nail in water I feel that the iron will not rust as the zinc will be protecting it from both oxygen and water by sacrificial protection. The zinc will react in its stead. *7 Galvanized nail in salted water I feel that the iron will not rust as the zinc will be protecting it from both oxygen and water by sacrificial protection. The zinc will react in its stead. *8 Iron nail with anhydrous calcium chloride + stopper I feel that the iron will not rust as the stopper will prevent any oxygen from coming in contact with the iron and the anhydrous calcium chloride will absorb the water. *9 Iron nail in air This experiment would probably show signs of rust after a long time as both oxygen and water can come in contact with the nail. I feel that it would not show much rust after a week. Results TEST TUBE NUMBER OBSERVATIONS AFTER ONE WEEK 1 Rust on the nail and on the sides and the bottom of the test tube.
My experiment had the same volume of water i.e. 10mls. The experiments marked with a star were carried out by some other members of the group and they had a different volume for their experiments. 3. The galvanized nails were put in later than the other nails because the college did not supply them when asked. 4. The galvanized nails were a different size and this could have had an effect on the experiment. The galvanized nails might have taken longer to rust because of the size. The oxygen and water had a larger area to work on. Conclusion My prediction was correct as I needed both air and water for the nails to rust. The salted water produced a much faster reaction as the salt acted as a catalyst for the reaction as did the sulphuric acid in the acid rain. I think that the experiment could have been improved by using more substances to prove that the corrosion of iron needs air and water. If I had increased the molarity of the acid, I feel the reaction would have been even faster. A day after I had started the test I checked on the experiment. I found that some of the nails were already starting to rust. This happened in test tubes numbers 4 and 10.
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