Corrosion, standard grade chemistry

Corrosion Standard Grade Chemistry Topic 12

WHAT IS CORROSION? ,[object Object],[object Object],[object Object],[object Object],[object Object],Potassium Iron Gold REATIVITY SERIES Concept Cartoons: Rusting

CHEMICALS FOR RUSTING Rusting requires OXYGEN and WATER Rusting is speeded up by SALT

RUSTING ,[object Object],[object Object],[object Object],Why did the water rise up the tube? How would the rate of the water rising compare if the wool had been soaked in water instead of acid?

CHEMISTRY OF RUSTING ,[object Object],[object Object],Iron + oxygen Iron(III) oxide ,[object Object],Writing ion-electron equation practice: Sodium atoms losing electrons to form sodium ions Sulphur atoms gaining electrons to become sulphur ions Copper(II) ions being reduced Bromine atoms being reduced Fe + O 2 Fe 2 O 3

CHEMISTRY OF RUSTING 2 ,[object Object],[object Object],Iron atoms into iron(II) ions Iron(II) ions into iron(III) ions Write ion-electron equations for both steps The IRON is OXIDISED

REDOX REACTIONS ,[object Object],[object Object],Oxygen and water 2H 2 O + O 2 + 4e 4OH - GAIN of electrons = REDUCTION The reduction step involves these chemicals: ,[object Object],[object Object]

DETECTING RUSTING ,[object Object],[object Object],[object Object]

TUTORIAL QUESTIONS ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Practical A Set up the experiment shown bellow, using two metals of your choice. Use a U-tube instead of a beaker.

TUTORIAL QUESTION Concentration of dissolved electrolytes Relative rate of rusting of iron ,[object Object],[object Object],[object Object]

FLOWING ELECTRONS ,[object Object],A Oxidation Reduction ,[object Object],Fe Fe 2+ + 2e

MORE REDOX A Iron Tin ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

MORE REDOX 2 A Iron Magnesium ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

TUTORIAL QUESTIONS ,[object Object],[object Object],[object Object],A Iron Carbon Electrons move from the carbon rod to the iron Electrons flow through the solution A blue colour appears at the iron electrode The mass of the iron electrode decreases The iron is oxidised Set up an experiment to answer the above questions.

PREVENTING CORROSION ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Carry out electroplating practical (7.2)

ELECTROPLATING Copper Gold Gold ions, Au + DC -ve +ve The metal to be coated is at the NEGATIVE terminal POSITIVE ions of the OTHER METAL are in the solution These ions are attracted to the negative terminal, and when they meet it turn into atoms So the copper is coated in gold atoms Write an ion-electron equation for the reaction occurring at the negative electrode Is this oxidation or reduction? Check-test 12.2 ext.

Cathodic Protection ,[object Object],[object Object],[object Object],[object Object],[object Object],Carry out Nails in Contact practical (7.3 core)

CHEMICAL PROTECTION ,[object Object],A Iron Magnesium A metal high in the electrochemical series is connected to the metal to be protected and is sacrificed - This is used in underground pipes Mg In terms of electrons, explain how sacrificial protection works.

TUTORIAL QUESTIONS ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

PRACTICE EXAM QUESTIONS SG textbook, p120-121 Questions for SG textbook, p43-44

Corrosion, standard grade chemistry

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