Flashcards in Chapter 3 - Electrolysis And Processes Deck (13):
Give a pneumonic for how to remember what oxidation and reduction does in electrolysis
Oxidation Is Loss Reduction Is Gain
This is handy as it is opposite to what is expected, reduction being gain
What charge is a cathode?
What charge is an anode?
Give a pneumonic to remember the charges of electrodes
Positive Anode Negative Cathode
This is apt as it is the point I would “Panic” as I begin to forget which way it is
What is electrolysis ?
The use of electricity to separate substances, ions
Why does electrolysis only work with ions? What state must they be in?
It only works with ions because it needs to be able to conduct electricity, this also means the ions must be in liquid state or aqueous so the ions can move
What is brine? What state is it?
Sodium chloride, sea water
It is aqueous, dissolved in water
How is electrolysis different with aqueous ions than liquid ions?
It has water, H2 O, molecules which separate to form H+ ions and OH- ions. The H+ ions go to the cathode and the OH- ions go to the anode.
What is the rule in aqueous electrolysis for what is formed at the cathode? Hint: think about hydrogen ions H+.
If the metal , say sodium, was more reactive in the reactivity series, which in this case it is, than hydrogen then a hydrogen gas would be formed/ discharged and the more reactive metal would stay in the solution. The least reactive ion is always discharged at the cathode. Hydrogen is usually formed as most metals are more reactive than it.
What is the rule in electrolysis for what is formed at an anode? Hint: think about Hydroxides and group 7 metals.
The formula for Hydroxide, therefore oxygen, is formed at the cathode unless the metal is a halogen (group 7), such as chlorine, then that is formed at the anode and the Hydroxide stays in the solution making the solution a something Hydroxide in most cases.
What is the half equation of a Hydroxide molecule when it meets the anode (in the case there is no halogen and it is discharged)
4OH- - 4e- —> O2 + 2H2 O
What is the half equation of a hydrogen if it is discharged at a cathode?
2H+ + 2e- —> H2