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Transcript of Electrolysis
Electrolysis of CuSO
Cathode reaction: Cu (aq) + 2e- Cu(s)
Anode reaction: 2H O(l) O (g) + 4H (aq) + 4e-
Students should see a deposit of copper forming on the cathode. This will often be powdery and uneven.
If the current used is much lower, then the solid coating is shiny, impermeable and very difficult to rub off; this process forms the basis of electroplating.
With carbon (graphite) electrodes, the oxygen usually reacts with the anode to form CO2.
If copper is used for the electrodes, the copper anode dissolves. The reaction is the reverse of the cathode reaction.
Results: Deposit of Copper on the Graphite rod
Bulb lights up
Electrolysis of CuBr2:
CLEAN UP TIME!!
Carbon electrodes after electrolysis
The process of decomposing a solution or a molten compound by passing an electric current through it.
used in refining gold, silver, copper, and tin, and for obtaining aluminum, sodium, magnesium, and other metals from their ores.
In the cell, the electrolytic solution or molten electrolyte is in contact with two solid conductors called electrodes.
When the product of decomposition is a metal, it is either deposited as a coating on one of the electrodes or precipitated as sludge.
Electrolysis is carried out in an electrolytic cell
Chemistry school book as reference
Thanks For Listening!
Things you should know!
Electroplating is the application of electrolytic cells in which a thin layer of metal is deposited onto an electrically conductive surface.
Did you know?
1785 – Martinus van Marum's electrostatic generator was used to reduce tin, zinc, and antimony from their salts using electrolysis.
1800 – William Nicholson and Anthony Carlisle (view also Johann Ritter), decomposed water into hydrogen and oxygen.
1807 – Potassium, sodium, barium, calcium and magnesium were discovered by Sir Humphry Davy using electrolysis.
1875 – Paul Émile Lecoq de Boisbaudran discovered gallium using electrolysis.
1886 – Fluorine was discovered by Henri Moissan using electrolysis.
1886 – Hall-Héroult process developed for making aluminium
1890 – Castner-Kellner process developed for making sodium hydroxide
Observations at the electrodes:
+ve Terminal: The Cathode
-ve Terminal: The Anode
2CuSO + H O 2Cu +2H SO +O
CuBr Cu + 2Br
Cathodic Reduction half reaction:
Cu + 2e- Cu
2 H O + 2 e- H + 2 OH
Anodic Oxidation half reaction:
2Br Br + 2e-
H O O + 2 H + 2e-
Cu Cu + 2e-
Net ionic equation:
Cu + Cu Cu + Cu
1. 2 copper strips
2. 50.00 mL of CuBr2 (dissolved in water)
3. A battery of 3V
4. Conducting wires
5. 250 mL beaker
6. Light bulb
The setup consists of 2 copper electrodes placed in a beaker filled with 50.00mL of the electrolyte CuBr2 (which is dissolved in water). These electrodes are connected to a battery of 3V as well as to a light bulb.
Each Cu rod is connected to a terminal of the battery thus there is a positive electrode, which is the anode, and a negative electrode which is the cathode. An electric current runs through the electrolyte CuBr2 to break it down into Cu2+ and Br-. As a result, the copper cations of the electrolyte are attracted to the negative electrode and the bromide anions are attracted to the positive electrode.
Movement of electrons: From anode to cathode, through the conducting wires. Thus they produce electricity that light up the bulb in the circuit.
Formation of a few gas bubbles
The anode loses mass
Exceptions: Electrolysis does not work on covalent compounds.
Electroplating is used to give metal objects a better appearance or to protect them from corrosion, wear, or rust. Tableware, trays, decorative pieces, and jewelry are plated with gold or silver to make them more attractive. Copper is coated with chromium to protect it from corrosion. For the same reason iron and steel are plated with nickel, chromium, tin, zinc, or cadmium. Tin cans, for example, are tin-plated steel, and the chrome trim on automobiles is chromium-plated steel. Platinum, palladium, and rhodium are used to coat other metals with a hard, corrosion-resistant surface.
Electrolysis of the aqueous solution copper(II) Bromide
The setup consists of 2 graphite electrodes placed in a U tube filled with 50.00mL of the electrolyte CuSo4 (which is dissolved in water). These electrodes are connected to two batteries of 3V as well as to a light bulb.
1. 2 Graphite (carbon) electrodes
2. 50.00 mL of CuSO4 (dissolved in water)
3. 2 batteries of 2V
4. Conducting wires
5. U Tube
6. Light bulb
Electrolysis of an aqueous solution is more complicated since water ions and Cu⌃2 and Br⌃- ions are both present in the solution.
There is a possibility of 2 elements to be formed at each electrode
However only the less reactive element will be formed.
Copper( II) Bromide solution ( 1M)
1- Connect two wires leads (different colors) attached to alligator clips to a direct current power supply.
2- Clean and mount the glass U-tube on a ring stand
3- Connect the alligator clips to the corresponding electrodes.
4- Fill the U-tube three fourth full with the Copper(II) Bromide solution
5- Insert the carbon electrodes into the solution and electrolyze
6- Observe any changes.
Musallam working on his electrolysis experiment
CuBr electolysis using Cu
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CuSO using both Cu and C!
Electrolysis ( General, History)
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CuBr using C