{"id":14932,"date":"2020-12-01T07:01:17","date_gmt":"2020-12-01T01:31:17","guid":{"rendered":"https:\/\/cbselibrary.com\/?p=14932"},"modified":"2020-12-01T14:28:14","modified_gmt":"2020-12-01T08:58:14","slug":"rusting-redox-reaction","status":"publish","type":"post","link":"https:\/\/cbselibrary.com\/rusting-redox-reaction\/","title":{"rendered":"Rusting as a Redox Reaction"},"content":{"rendered":"
<\/p>\n
Corrosion of metal:<\/span> People also ask<\/strong><\/p>\n Controlling rusting:<\/strong> 1. Using protective coating 2. Alloying 3. Sacrificial protection<\/strong><\/span><\/p>\n Aim:<\/strong> To investigate the effect of other metals on rusting. Results: Discussion:<\/strong><\/p>\n Conclusions:<\/strong><\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" Rusting (Corrosion) as a Redox Reaction What is corrosion of a metal? Corrosion of metal: When metals are exposed to their environment, they undergo corrosion. For example, after some time, a shiny aluminium pot will lose its shine, silverware will tarnish and an iron structure will rust. Corrosion of metal is a redox reaction … Read more<\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":""},"categories":[84],"tags":[5939,5941,5944,5943,5938,5936,5903,5904,5942,5905,5937,5906,5935,5940],"yoast_head":"\n
\n<\/strong><\/p>\n\n
\nM \u2192\u00a0Mn+<\/sup> + ne–<\/sup><\/li>\n
\n(a) Electropositivity of metals
\n(b) Nature of the product of corrosion<\/li>\n
\n
\n<\/strong><\/li>\n
\nWhen a metal corrodes, it usually forms an oxide coating.
\n(a) The oxide coating of aluminium, for example, is tightly packed, non-porous and is firmly attached to the metal. It does not let water and air penetrate through it, protecting the aluminium underneath from further corrosion. This explains why aluminium is quite resistant to corrosion even though it is very electropositive. Other metals with similar protective oxide coating<\/strong> include nickel, chromium, tin, lead and zinc.
\n(b) The oxide coating of iron on the other hand, is not tightly packed, porous, weak and easily peels off. Thus, water and air can penetrate through the coating to further corrode the iron metal underneath it.<\/li>\n
\n<\/li>\n<\/ul>\n\n
Rusting as a redox reaction<\/strong><\/h3>\n
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\n<\/li>\n
\n<\/li>\n
\n<\/li>\n
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\n<\/li>\n
\nFor example:
\n(a) Iron structures such as bridges, fences and cars at coastal areas rust faster due to the presence of salts in the coastal breeze.
\n(b) Iron structures in industrial areas rust quickly as these areas have air polluted with acidic gases such as sulphur dioxide and nitrogen oxides.<\/li>\n<\/ul>\nOther metals and rusting of iron<\/strong><\/h3>\n
\n
\n<\/li>\n
\n<\/li>\n
\n<\/li>\n<\/ul>\nWhat are some ways of preventing corrosion of metals?<\/strong><\/h3>\n
\nGenerally, there are three main ways to control rusting.
\n<\/p>\n
\n<\/strong><\/span>The protective coating prevents water and air from reaching the surface of iron. Various materials can be used as the protective coating, depending on the costing and usage of the iron items.<\/p>\n\n
\n
\n<\/li>\n<\/ul>\n<\/li>\n\n
\n<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n
\n<\/strong><\/span>Stainless steel<\/strong> is a corrosion resisting alloy of iron.<\/p>\n\n
\n
Effect of other metals on rusting\u00a0experiment<\/strong><\/h3>\n
\nProblem statment:<\/strong> How do different types of metals in contact with iron affect rusting?
\nHypothesis:<\/strong> When a more electropositive metal is in contact with iron, the metal inhibits rusting. When a less electropositive metal is in contact with iron, the metal speeds up rusting.
\nVariables:<\/strong>
\n(a) Manipulated variable : Different metals in contact with iron
\n(b) Responding variable : Presence of blue colouration
\n(c) Controlled variables : Clean iron nails, medium in which iron nails are kept, temperature
\nOperational definition:<\/strong>
\nBlue colouration indicates rusting of iron.
\nMaterials:<\/strong> Iron nails, magnesium ribbon, copper strip, zinc strip, tin strip, hot jelly solution containing a little
\npotassium hexacyanoferrate(III) solution and phenolphthalein indicator, sandpaper.
\nApparatus:<\/strong> Test tubes, test tube rack.
\nSafety measure:<\/strong>
\nPotassium hexacyanoferrate(III) solution is poisonous. Thus, the hot jelly solution should be handled with care.
\nProcedure:
\n
\n<\/strong><\/p>\n\n
\n<\/strong><\/p>\n\n\n
\n Test tube<\/strong><\/td>\n Pair of metals<\/strong><\/td>\n Intensity of dark blue colouration<\/strong><\/td>\n Pink colouration<\/strong><\/td>\n Inference regarding rusting<\/strong><\/td>\n<\/tr>\n \n I<\/td>\n Fe only<\/td>\n Low<\/td>\n Present<\/td>\n The iron nail rusts a little.<\/td>\n<\/tr>\n \n II<\/td>\n Fe + Mg<\/td>\n None<\/td>\n Present<\/td>\n The iron nail does not rust.<\/td>\n<\/tr>\n \n III<\/td>\n Fe + Cu<\/td>\n Very high<\/td>\n Present<\/td>\n The iron nail rusts very quickly.<\/td>\n<\/tr>\n \n IV<\/td>\n Fe + Zn<\/td>\n None<\/td>\n Present<\/td>\n The iron nail does not rust.<\/td>\n<\/tr>\n \n V<\/td>\n Fe + Sn<\/td>\n High<\/td>\n Present<\/td>\n The iron nail rusts quickly.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n \n
\n(a) Magnesium is more electropositive than iron. This means that magnesium can lose its electrons more readily than iron. Therefore, magnesium is oxidised. Magnesium acts as the anode.
\n
\n(b) The electrons flow to iron which acts as the cathode. At the cathode, the electrons are gained by
\noxygen. Thus, oxygen undergoes reduction, producing hydroxide ions which give pink colouration with phenolphathalein.
\n
\n(c) The iron nail does not corrode. This explains the absence of blue colouration in this test tube.<\/li>\n
\n(a) Iron is more electropositive than copper. This means that iron can lose its electrons more readily than copper. Therefore, iron rusts or is oxidised. Iron acts as the anode.
\n
\n(b) Since iron and copper have a large difference in electropositivity, the rusting of iron occurs very quickly, producing a large amount of iron(II) ions. This explains the high intensity of blue colouration in this test tube.
\n(c) The electrons flow to copper which acts as the cathode. At the cathode, the electrons are gained by oxygen, thus reducing oxygen to hydroxide ions. The presence of hydroxide ions is indicated by the pink colouration.<\/li>\n
\nSimilar to test tube II, the iron nail in this test tube does not corrode, thus no dark blue colouration is found.
\nZinc acts as the anode and is oxidised as zinc is more electropositive than iron.
\n<\/li>\n
\nSimilar to test tube III, the iron nail acts as the anode and rusts. This is because iron is more electropositive than tin.
\n
\nHowever, the rate of rusting in test tube V is lower than that in test tube III as the difference in electropositivity
\nbetween iron and tin is smaller than the difference in electropositivity between iron and copper.<\/li>\n<\/ol>\n\n