sc10, electrolysis (paper 1) Flashcards
define electrolysis
when electrical energy from a direct current supply decomposes an electrolyte
define electrode
a rod made of metal/graphite which carries the current into or out of the electrode
define electrolyte
an ionic compound in a molten or dissolved in water state
what is the cathode
negative cathode
what is the anode
positive cathode
which electrode is the anion attracted to
anode
which electrode is the cation attracted to
cathode
at what electrode does reduction occur at
cathode
at what electrode does oxidation occur at
anode
in terms of electrons and oxygen, what happens in oxidation
- gains oxygen
- loses electrons
in terms of electrons and oxygen, what happens in reduction
- loses oxygen
- gains electrons
why can we only use electrolysis in liquids and solutions and not solids
the ions are free to move and carry the charge where as a solid cannot
what do we do befor electrolysing an insoluble ionic compound
- purify (if needed)
- mix with cryolite to lower melting point (if needed)
- then melt it to molten state
what happens when the ion is conducted to the compatible electrode
they are discharged as neutral atoms (solid/gas/molten)
how do we use electrolysis on soluble ionic compounds
we can dissolve them in water
explain why using electrolysis on soluble ionic compounds is more complicated
water splits into hydroxide and hydrogen ions
which electrode is hydroxide attracted to
anode
which electrode is hydrogen attracted to
cathode
does the cathode attract metal or non-metal
metal
does the anode attract metal or non-metal
non-metal
what determines which element will be discharged at the anode for aqueous solutions
hydroxide with always discharge unless a halide is present (fluoride, chloride, bromide, iodide)
what determines which element will be discharged at the cathode for aqueous solutions
the least reactive ion will be discharged
metals less reactive than hydrogen are: copper, silver, gold, platinum
