Chapter 7 Electrolysis Flashcards
How does electricity travel
Negative to positive
What is a conductor
a substance that allows electricity to pass through
What is an insulator
A substance that doesn’t let electricity pass through
Why can conductors conduct
Because they have free electrons
What are the solid conductors
Carbon (graphite)
Metals
What is decomposition
The breaking down of a compound
What is electrolysis
The decomposition of an ionic compound, when molten or in aqueous solution, by passing electric current.
What is an electrolytic cell
The entire set up of apparatus in electrolysis
What is the positive electrode called
What is the Negativeelectrode called
Anode (+)
Cathode (-)
What is the electrolyte
The liquid that undergoes electrolysis
Which electrodes are inert electrodes
Platinum
Carbon
What are inert electrodes
Electrodes that remain unchanged, but can carry current.
Why does decomposition occur
Electrons flow from negative to positive
In the liquid, ions carry the current. The ions move to the electrode of opposite charge hence current is transferred between electrodes through the solution.
Which ion moves to which electrode and what is carried out there
Cations - Cathode - Reduction
Anions - Anode - Oxidation
What are the 4 poss substances (reactivity series)that form at the cathode in the electrolysis of an aqueous solution and why?
Hydrogen (H)
Copper (Cu)
Silver (Ag)
Gold (Au)
They are less reactive.
At anode what forms in a dilute solution and half equation
Oxygen would form
4OH- —-> 2H2O + O2 + 4e
Half equation for water
H20 —> H+ + OH-
At anode what forms in a concentrated halide solution
and the three halides that could form
The halogen forms
Bromine
Iodine
Chlorine
What if there is no halide in the solution, then what forms
Oxygen
What does RAC stand for
Reduction At Cathode
Other uses of electrolysis
Metal refining
electroplating
What is electroplating
Using electricity to coat one metal with another to make it look better or prevent corrosion.
General set up for electroplating (cathode, anode, electrolyte)
Cathode - Object to be electroplated
Anode - Metal X
Electrolyte - A solution of soluble compound X
in which solution do halogens get discharged
concentrated
in a refining which electrode has the pure metal
negative electrode
cathode
in a refining which electrode has the impure metal
positive electrode
anode
which types of elements go to the cathode
metals and hydrogen to get reduced
which types of elements go to the anode
non-metals to get oxidised
how can we use electrolysis to determine which metal is more reactive between 2 metals e.g manganese or magnesium
set up a magnesium/ manganese cell
the electrode that loses mass is more reactive
how do electrons flow
negative to positive
Explain, in terms of electron transfer, why the more reactive metal is always the negative
electrode.
metals react by losing electrons
the more reactive metal will lose electrons more readily (making the electrode negatively charged)
in conc aqueous what comes at anode
halogen
How are electrons carried across the cell
> wires and electrodes
solution
wires and electrodes - electrons
solution - ions
