5. Electricity And Chemistry Flashcards
What is the conditions for electrolysis?
Only works for ionic compounds when they are molten or dissolved in water - they only conduct electricity when in these states
What is electrolysis?
Breaking down of a compound using an electric current
What is electrolyte?
Compound that conducts electricity when molten and breaks down during electrolysis
What is electrode?
Rods that carry the electric current to and from the electrolyte
What are electrodes made of and why?
Normally made from inert conductor such as graphite or platinum so the electrodes don’t react with the electrolyte or the product of electrolysis
What is the positive electrode called?
Anode
What is the negative electrode called?
Cathode
Products of the electrolysis of molten lead bromide and half equations
Anode: Br2
2Br- => Br2 + 2e-
Cathode: Pb
Pb2+ + 2e- => Pb
Concentrated Hydrochloric Acid
Half equations and products
Anode: Cl2
Cl- => cl2 + 2e-
Cathode: h2
2h+ + 2e- => H
Concentrated aqueous sodium chloride (brine)
Products and half equation
Anode: H2
2H+ + 2e- => h2
Cathode: cl2
Cl- => cl2 + 2e-
The ions remaining in solution are na+ and oh-
-> an aqueous solution of sodium hydroxide is formed
Discharge series for positive ions
From less to more likely
Na mg al h cu
Discharge series for negative ions
So4 no3 oh cl br i
Describe the preparation for purifying of copper
Anode: impure strip of copper
Cathode: thin strip of pure copper
Electrolyte solution: copper(II) sulfate
Describe the process for purifying of copper
Anode: copper atoms lose their valency electrons and form copper ions. These go into solution as part of the electrolyte
Cu -> cu2+ + 2e-
Cathode: copper ions gain electrons and from copper atoms. They are deposited on the strip of pure copper
Cu2+ + 2e- -> cu
What is the uses of electroplating?
Protect metal from corrosion
Improve the appearance
State the electrolyte, overall equation, and cathode anode material for extracting aluminum
Electrolyte: cryolite NaAlF6
Overall equa. 2al2o3 -> 4Al + 3o2
Made of carbon
Describe the process of extracting aluminium
Cathode: al ions gain electrons and are reduced to al metal. The liquid al metal falls to the bottom of the cell. It is removed using siphon tube
Al3+ + 3e- => al
Anode: oxide ions lose electrons and are oxidised to oxygen
2o2- =>o2+4e-
The O2 react with hot carbon anodes -> form co2 -> carbon anode burn away
What is conductor
Substances which have low resistance to the passage of electricity
Why is copper used in electrical wiring
Good conductor of electricity
Easily drawn into wires - ductile
Easily purified by electrolysis
Why is steel is used as core?
Gives cable additional strength to stop them sagging and breaking
Why is aluminum used in wire?
Good conductor of electricity
Low density
Resistant to corrosion
Why is plastic used as an insulator?
Don’t conduct electricity, flexible, non-biodegradable
-> useful for covering electrical wire -> dont get electric shock
Why is ceramics used as insulator
Dont conduct electricity
High melting point -> do not melt when high electricity current flow
Not affected by water or air
Can be moulded into complex shape
