C6 Flashcards
what is electrolysis
the splitting up of a substance using electricity
why does electrolysis need to be carried out as a molten or dissolved solution
as when it’s molten or dissolved the particles are allowed to move so electricity can flow
what charge is the anode
positive
what charge is the cathode
negative
what an electrolyte
the substance being broken own by electrolysis
which electrode do the negative charged ions go to
the anode (positive node)
which electrode does the positively charged ion go to
the cathode (negatively charged node)
what’s a positive ion called
cations
what’s a negative ion called
anions
what is oxidation
loss of electrons
gain of oxygen
what is reduction
gain of electrons
loss of oxygen
where does reduction happen
at the cathode
where does oxidation happen
at the anode
give the half equation for Mg 2+
Mg2+ + 2e- —-> Mg
what is always produced if an aqueous solution is electrolysed
H+
OH-
the electrolysed electrolyte
give the equation for water undergoing electrolysis
H20 = H+ + OH-
= the symbol for a reversible reaction
what are the 2 rules for aqueous electrolysis
rule 1: the least reactive positive cation (positive ion) will be DISCHARGED at the cathode.
rule 2: if a halide is present as one of the negative anions (negative ion) then that would be DISCHARGED at the anode as a gas. If no halide is present then the OH- will be oxidised and would be DISCHARGED at the anode as 02 gas.
what happens to the H+ and OH- ions at the end of the electrolysis
they react together to form water (pani [pronounce p-ah-knee])
name the reactivity series in order with carbon and hydrogen
potassium
sodium
calcium
magnesium
aluminium
carbon
zinc
iron
tin
lead
hydrogen
copper
silver
gold
platinum
name the formula for a nitrate ion
NO3 -
name the equation for a hydroxide ion
OH 1-
name the equation for a sulphate ion
SO4 2-
name the formula for a hydrogen ion
H 1+
name the equation for a carbonate ion
CO3 2-
name the equation for an ammonium ion
NH4 1-
what is a base
anything that can neutralise an acid
what are the 2 types of bases
there are the insoluble ones: alkaline
and the non-insoluble ones
what do all alkaline have in common
they all contain OH- ions
what do alkalis do when they are dissolved
they undergo ionisation
what do all acids have in common
they all have H+ ions in them
what process does acids undergo when they are dissolved in water
ionisation
name the steps in extracting aluminium
- open cast mining - bauxite ore is dug up. rocks from that ore is removed leaving behind aluminium oxide
- cryolite is added to the aluminium oxide to lower the melting point of aluminium oxide. it’s then melted down.
- the outside wall of the electrolysis tank acts like a cathode so the aluminium forms at the walls and falls to the bottom of the tank.
