Electrochemistry Flashcards
Explain with the aid of a labelled diagram how impure copper is purified by electrolysis
Copper sulfate acts as electrolyte with a battery as a power supply
The impure copper is oxidised and is attached to anode
The pure copper acts as a cathode and the copper ions (Cu2+) in solution are reduced
Write balanced equations for the reactions that take place at the electrodes for the electrolysis of copper
Cu2+ + 2e¯→ Cu
Cu → Cu2+ + 2e¯
What happens to impurities in the copper during electrolysis?
Falls to bottom of container
Name a material suitable for use as the electrodes
Platinum
How was the current conducted through the electrolyte?
Movement of ions
In the electrolysis of aqueous sodium sulfate, what is the ratio for the cathode : anode
cathode : 2
anode : 1
In the electrolysis of aqueous sodium sulfate, write the equation at the anode and cathode
Anode - 2H20 -> 2H+ +2é + O2
Cathode - 2H+ +2é -> H2
In the electrolysis of aqueous sodium sulfate, when a current passed through the electrolyte for 15 mins, 8.5 cm^3 of gas was collected above positive electrode. What volume of gas was collected above the negative electrode in the same time?
8.5 x 2 =17
In the electrolysis of aqueous sodium sulfate, at which electrode did a purple/blue colour appear and why? And at which electrode did a pink colour appear and why?
Purple/blue -> Cathode, OH- ions generated (basic)
Pink -> Anode, H+ ions generated
In the electrolysis of potassium iodide, write balanced half equations in both electrodes
Anode - 2I- -> I2 + 2é
Cathode - 2H+ +2é -> H2
In the electrolysis of potassium iodide, explain the colour change at the anode and cathode
Anode - Red/brown colour due to Iodine produced
Cathode - Pink due to H+ ions generated
In the electrolysis of Acidified water, which species is oxidised?
H20
In the electrolysis of acidified water, write the half balanced equations at anode and cathode
Anode - 2H20 -> 2H+ +2é +O2
Cathode - 2H+ +2é -> H2
In the electrolysis of acidified water, what is observed?
Bubbles of oxygen and hydrogen being released at the electrodes
In the electrolysis of acidified water, what are the products?
Oxygen gas and hydrogen gas
Explain with the aid of a labelled diagram the electrolysis of acidified water
acidified h20 [H2SO4] which acts as an electrolyte with a battery as a power supply
The H2O is oxidised and is attached to anode
The H+ ions are reduced at the cathode
In the electrolysis of aqueous sodium sulfate, what are the products?
Oxygen gas
Hydrogen gas
Explain with the aid of a labelled diagram the electrolysis of sodium sulfate
Dilute Na2SO4 acts as an electrolyte with a battery as a power supply
The H20 is oxidised and is attached to anode
The H+ are reduced at the cathode
In the electrolysis of potassium iodide, what are the products?
Iodine
Hydrogen gas
In the electrolysis of potassium iodide, what indicator is added?
Phenolphthalein (pink in alkaline conditions)
In the electrolysis of sodium sulfate, what indicator is added?
Universal indicator
Explain with the aid of a labelled diagram the electrolysis of potassium iodide
Dilute Pottasium iodide acts as an electrolyte with a battery as a power supply
The I- ion is oxidised and is attached to anode
The H+ ion are reduced at the cathode
In the electrolysis of potassium iodide, what is the role of K+ ions
They are spectator ions as they are too stable to be discharged
For the electrolysis of copper sulfate, what are the products?
Purified copper
What occurs/is observed in the anode when the Cu is oxidised
The anode disintegrates
The copper is being converted into ions and dissolving into the solution
What occurs/is observed when Cu2+ is reduced?
Cathode builds up with pure copper deposited
The copper ions from solution are being converted into copper atoms depositing into anode
What is electrolysis?
Breaking up of a substance due to the passage of an electric current though it in an aqueous solution or when molten (coined by Faraday)
What is an electrolyte?
Substance that causes electricity as it has ions that can move
What are inert electrodes?
Electrodes do not react with the electrolyte
What are active electrodes?
Electrodes that do react with the electrolyte they are in
Where does oxidation occur
Anode
Where does reduction occur?
Cathode
What is electroplating and give examples
Process where electrolysis is used to put a layer of one metal on the surface of another metal
Gold plating [jewellery], EPNS nickel cutlery can be pated with silver [cutlery]
