ELECTROCHEMISTRY

Question 1

ECM

Answer 1

• electrochemical machining
• reverse electroplating
• helps give better detail; more intricate and delicate parts

Question 2

Oxidation

Answer 2

loss of electrons

Question 3

Reduction

Answer 3

gain of electrons

Question 4

3 Parts of a Battery

Answer 4

1. Anode
   a) negative electrode that releases electrons
   b) oxidized electrode (electrode where oxidation occurs)
   c) current: Anions flow toward the anode
2. Cathode
   a) positive electrode that accepts electrons
   b) the reduced electrode (electrode which reduction occurs)
   c) current: cations flow toward the cathode
3. Salt Battery
   a) separates cathode and anode
   b) contains electrolytes (ions)
   c) prevents build up of excess charges at the electrodes (charge buildup will cause the reaction to stop

Question 5

What is required for electroplating to occur?

Answer 5

1. Roughen the object
2. The cation in the electrolyte bath has to be the same as the metal you’re plating with
3. The object to be plated must be connected to the negative terminal

Question 6

Practical Examples of Plating/Electroplating in Manufacturing

Answer 6

1. Manufacture mirrors; plate with silver
2. Create alloys esp. brass; easier than mixing molten metals Cu/Zn plating
3. Jewelry or watch cases; silver or gold plating
4. Silverware; silverplating
5. Machinery; Strengthen flexible metals like steel with chromium, nickel, or copper
6. Truck bumpers; strengthen flexible metals like steal with chromium, nickel, or copper
7. Electronics; to carry current and/or for corrosion resistance using nickel plating
8. Electronic circuits; gold plated
9. Decorate hubcaps; chrome or nickel plated
10. Galvanized nails; nickel or zinc plating to prevent corrosion
11. Steel cans; plate with tin for better storage
12. Engine bearing; plated with silver
13. Appliances; decorative handles are nickel or chromium plated
    5.
    6.
14. چ

Question 7

1/2 Reaction Equations

Answer 7

• If electrons in product, OXIDATION

- if electrons in reactant, REDUCTION

Question 8

Electricity

Answer 8

electrons generated at the anode flow toward the cathode

Question 9

Simple CIrcuits

Answer 9

• Circuit Types
  a) Series- only one path for the current to travel
  b) Parallel- multiple pathways for the current to travel
  I

Question 10

Advantages to a Series Current

Answer 10

• (because less current)
  a) safer
  b) battery lasts longer
  c) easily turned off by disconnecting any part of it

Question 11

Disadvantages of a Series Circuit

Answer 11

• if one bulb goes out, they all go out

- adding more loads lowers the currents in all the connected loads which decreases the performance

Question 12

Advantages to Parallel

Answer 12

• when one lightbulb goes out, the others remain lit

- there is a continued performance of appliances when one is added or removed from the circuit

Question 13

Disadvantages to Parallel

Answer 13

• more current is drained from the power source with the addition of a new load
• could cause the fuse to blow
• reduces battery life

Question 14

Electroplating

Answer 14

a process of depositing a thin layer of a fine and superior metal (like chromium, zinc, nickel, gold, etc.) over the article of a base and cheaper metal (like iron, copper), often with the help of electric current

Question 15

Electroplating Purpose

Answer 15

primarily used for depositing a layer of a material to bestow a desired property (like abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities) to a surface that otherwise lacks the property. For example, some metals are recognized for strength, while some are recognized for their beauty; when both are desired, one could coat, for example, strong iron with a more attractive metal, like gold or silver.

• also could be used to build up thickness or undersized parts
• used to economically change the physical appearance of substances

Question 16

Plating

Answer 16

surface covering in which a metal is deposited on a conductive surface

TWO TYPES:

• electroless plating
  a) also known as chemical or auto-catalytic plating; is a non-galvanic type of plating method that involves several simultaneous reactions in an aqueous solution, which occur WITHOUT the use of external electrical power
• electroplating
  a) an ionic metal is supplied with electrons to form a non-ionic coating on a substance

Question 17

Electrochemistry

Answer 17

the study of the interchange of chemical and electrical energy

Question 18

Oxidation-Reduction Reactions

Answer 18

• driving force is electron transfer

Question 19

Build a Dry Cell Battery

Answer 19

• type: aluminum air battery

aluminum: oxidized at the anode
oxygen in air: reduced at the cathode
activated charcoal: gives the reaction a surface on which to occur
sodium chloride soaked filter paper: salt bridge

Electrons travel from aluminum foil anode on the outside of the battery. Electrons travel through the cables toward the cathode (oxygen). At the cathode, the oxygen in air pockets is reduced by the electrons. Anions and cations travel through the salt bridge to the anode and cathode, respectively, to prevent charge build up.p

Question 20

Electric Cells

Answer 20

• change chemical energy into electric energy
• Parts
  a) Two electrodes (anion and cathode) - metals
  ; each has a voltage
• voltage: a push of electrons in an electric current

To find potential difference, subtract separate voltages

Question 21

Potato Clock

Answer 21

• Two Metals
  a) Zinc
• voltage is - 0.76
• more reactive than Cu because voltage is lower
• dissolves in electrolyte so Zn loses e-, becomes negative terminal because e- build up on the Zn electrode
  b) Coppper
• voltage is 0.34
• loses e- to H+1 in electrolyte to produce hydrogen gas, becomes positive terminal

Potential Difference is 1.1 volts (absolute value)

• Electrolyte
  a) Potato- juice- aq solution
  b) lemon- citric acid

Current Flow

a) electrons from the Zn electrode (anode) move through wire to Cu electrode (cathode) to replace the e- that Cu is losing to H
b) the flow produces current that powers the clock

Ion Flow

a) Zn+2 ions move through the electrolyte to the copper electrode to regain e-
- Zn electrode shrinks in size
- Cu electrode turns back due to Zinc metal plating on it

Net Result
- both metals under go oxidation then reduction as the electric cell operates

Question 22

Zinc Plating: Gold Rush

Answer 22

• brass alloy
  a) copper/zinc mixture makes brass
  b) zinc is reduced and oxidized
• Granular zinc to zinc ion (ox) to zinc metal plated on Cu (red)
  c) copper- electrochemical potential and plating surface
• different percentages create different colors of brass
  a) “silver” from high (45%) zinc concentration on exterior surface
• Granular zinc dissolves in sodium hydroxide to form zinc ions from solution migrate to the surface and get reduced to granular zinc. This metallic zinc plates onto the copper surface
• Beta
  b) “gold” from lower (35%) zinc concentration on exterior surface
• when the zinc coated penny is heated, the zinc migrates THROUGH the copper
• Alpha

Question 23

Electroplating a Spoon

Answer 23

(MEMORIZE PIC)

explanation: Electrons at the cathode attract the copper cations (reduction), copper deposited on spoon

Ox/Red Flow

a) Cu ions in the salt solution are reduced at the cathode so that copper metal is deposited on the spoon (copper coating)
b) copper is oxidized at the anode to replenish the supply of copper ion in the salt solution so that the electroplating continues

Question 24

Silver Mirror (silverplating)

Answer 24

• Silver is reduced (you could see the solution discolor and eventually deposit on the glass walls)
  a) Ag starts as ion in silver nitrate and ends as the neutral element on the walls of the glass
• Sugar is oxidized
  a) glucose is converted to gluconic acid