16.6 –16.7: Corrosion, Electrolysis

• The rate of corrosion can be increased by factors such as oxygen, moisture, temperature, acidity, saltwater, and bacteria.
• Corrosion is the gradual destruction or deterioration of metals due to chemical reactions with their environment.
• Metal objects that are exposed to air will eventually rust because iron reacts with water and oxygen to form hydrated iron(III) oxide (rust).
• A cell is dead because they are at equilibrium
• What is electrolysis?

  Drive a reaction in a non-spontaneous direction with an external power source, voltage appears in a spontaneous direction at e-flows
• What are some examples of electrolysis?

  Water, copper sulfate solution, and molten sodium chloride.
• In electrolysis, electrons flow from the negative terminal through the wire into the metal object being plated, forming positive ions in the process.
• Electroplating involves using electricity to deposit one type of metal onto another.
• The positive ions move towards the cathode where they gain electrons and become neutral atoms again.
• At the same time, the negative ions move toward the anode where they lose electrons and become positively charged ions again.
• In a spontaneous direction, are electrons flowing in or out

  electrons will spontaneously flow to the electrode of the cell with the greatest reduction potential
• What is an anode?

  Positive electrode.
• What is a cathode?

  Negative electrode.
• What is an electrode?

  A conductor through which electricity enters or leaves an object, substance, or region.
• Directions of reactions that produce gas need lots more voltage than just Ecell to drive (Takes alot more force)
• Larger batteries (were reactants) can do more ___

  work
• Moles transferred depends on moles of ___ used

  reactants
• Q = nF, what does Q stand for

  Charge transfered
• Q = nF, What does n stand for?

  number of e- transfered
• Q = nF, what does F stand for?

  Faraday's constant
• What does A stand for

  Ampere
• What is corrosion?

  redox reactions (have to be spontaneous) that degrade material (metals) (ex: rusting of ferrous metals)
• 1 A =

  1 C/s
• To find t, what's the equation you use in relation to Q and A

  t=Q/A
• What does Q = A * T mean

  Q=amount of electron charge transported, I=ampere, t=time
• Welec = nFE = -deltaG. What does each species stand for?

  F = faraday's constant, E = cell potential (not necessarily under standard conditions), n = number of moles e- transferred through circuit (connected to time, current and mass of species in redox).
• Reactions that happen: Any pair of reactions involving available reactants where l E1- E2 l < applied. Prevented by...

  Over potential (larger for gas production), low concentration of reagent
• Reaction goes in a non-spontaneous direction (highest reduction potential goes as an oxidation) (lowest goes as written)
• In a galvanic cell, the metal with lower reduction potential is called the anode, while the one with higher reduction potential is called the cathode.
• When two metals are placed together in contact with an electrolyte solution, they form a galvanic cell.
• What are ways to prevent corrosion?

  Paint to coat and protect from exposure to water and air, create alloys that don't corrode easily (ex: stainless steel),
• Al is self-protecting because Al2O3 is dense and hard
• What is anodization?


  Plate out a sacrificial metal that more easily acts like paint and can provide cathodic protection when scratched
• mols to mmol


  divide by 1000
• mols to umols


  10^-6 caculation
• grams to mg


  Multiply by 1000