C10-12 ELECTROLYSIS METALS , REVERSIBLE REACTIONS Flashcards
electrolysis
using direct current to break compounds down their elements
electrolyte
liquid used for electrolysis because ions can move - either molten or dissolved ionic compounds
electroylsis of solids
does not work as ions can’t move
electrodes
conducting rods placed in electrolyte , connect to power supply
cathode
negative electrode where cations + are discharged
anode
positive electrode where anions - are discharged
oxidation HT
loss of electrons OIL
reduction HT
gain of electrons RIG
anOx
Anode is for Oxidation
caRe
CAthode is for Reduction
half equations
an equation that shows what happens to just one of the ions during chemical reaction. Two half - equations combine to give the overall ionic equation
half equations in electrolysis
show electron transfer
cathode (reduction):
m+ + e - m
anode (oxidation):
x - X + e-
electrons in half equations
cations will gain the same number of electrons as their charge. anions will lose the same number of electrons as their charge
non-metals in half equations
most non-metals will form molecules : O2 , F2 , CL2, BR2 , L2 etc
so you will need two of them in the half equation
discharged
when an ion loses its charge to become an atom
electrolysis of molten salts
cathode: metal
anode: non-metal
ions in salt solutions
metal, non-metal and H+ and OH- because water partially ionises
hydrogen half equation
2H+g + 2e- -> H2g
electrolysis of salt solutions cathode
metal unless reactive metal such as K, Na ,Li , Ca in which case hydrogen
electrolysis of salt solutions anode
non metal unless sulphate salt in which case oxygen
electroylsis of sulfuric acid
cathode: hydrogen
anode: oxygen
purifying copper set up
anode: impure copper
cathode: pure copper
electrolyte: coppe sulphate solution
purifying copper explanation
copper atoms leave the anode
(cu - cu2 + 2e-) travel through solution and go to cathode (cu2 + 2e- -> cu)
impure atoms on the anode fall to the bottom as sludge
reactivity series (most to least)
potassium , sodium , calcium , magnesium , aluminum , zic , iron , copper , silver , gold
forming cations
the more relative metals more easily lose electrons to form cations
forming cations
the more reactive metals more easily lose electrons to from cations
reaction with cold water H20 l
metal + water - metal hydroxide + hydrogen
potassium - violently
sodium - very quickly
calcium - slowly
reaction only with steam
metal + water - metal oxide + hydrogen
magnesium , zinc , iron
no reaction with water or steam
copper , sliver , gold
reaction with acid
metal + acid -nsalt + hydrogen
sodium, potassium - violent
calcium magnesium , zinc , iron - steady
coper , sliver , gold - no reaction
displacement acid
reactions in which a more reactive metal displaces a less reactive metal from a salt e.g.
copper sulfate + zinc -> zinc sulfate + copper
does not work backwards as copper is less reactive than zinc
redox reactions
reactions in which an oxidation and reduction happen at the same time , such as displacement reactions
redox during displacement
the more reactive metal gets oxidised e.g.
Zn - Zn2+ + 2e-
the less reactive metal gets reduced e.g.
cu2+ +2e- -> cu
spectator ion
an ion that does not change during a chemical reaction
native state
when metals are found naturally in their pure from such as silver and gold
ore
rock containing enough of a metal compound to extract for profit . normally oxides or sulphides of the metal
extracting metals by heating with carbon
for extracting less reactive metals such as zinc , iron, copper. works because carbon is more reactive, e.g.. iron oxide + carbon - carbon dioxide + iron
extracting metals by electrolysis
done with metals more reactive than carbon such as potassium, sodium, calcium , magnesium, aluminium, e.g:
aluminium oxide - aluminium + oxygen
bioextraction
using living organisms to extract metals
bleaching
growing bacteria on poor quality copper ore. the bacteria produce a solution of copper sulphate from which copper can be extracted by electrolysis
phyoextraction
plants are grown that absorb metal compounds as they grow. the plants are then burnt to produce ash that is rich in metal compounds
oxidation
gaining oxygen
reduction
losing oxygen
redox
when reduction and oxidation reactions happen together
reduction of iron
iron produced from iron oxide by heating with carbon:
iron oxide + carbon - carbon dioxide + iron
iron is reduced, carbon is oxidised
reduction of aluminium ore
aluminium is produced from aluminium oxide by electrolysis:
aluminium oxide - alluminium + oxygen
aluminium is reduced , oxygen is oxidised
corrosion
when metals slowly react with oxygen , making them weaker
rates of corrosion
more reactive metals corrode more quickly
tarnish
a protective layer of oxide that stops the layers below from corroding
recycling
converting old waste metal into new metal that can be reused
advantages of recycling
natural reserves last longer less pollution from mining less pollution from processing less waste in landfill often less energy used
disadvantages of recycling
can be expensive
can use a lot of energy in transporting, collecting and sorting
life-cycle assessment LCA
looks at environmental impact of all stages of a products lifecycle, we should aim to reduce all damage
LCA stages
obtaining and processing raw materials
making and packaging the product
using the product
disposal or recycling of the product
reversible reaction
reactions that can go forwards as well as backwards (with products turning back into reactants)
dynamic equilibrium
the point at which the rate of the forwards reaction and backwards reaction are equal, so the concentrations of reactants and products stops changing
closed systems
nothing can escape, so dynamic equilibrium can be reached
open systems
gases can escape so dynamic equilibrium can’t be reached
equation for making ammonia
nitrogen + hydrogen = ammonia
N2 + 3H2 = 2NH3
exothermic
hater process
for making ammonia in factories:
-200 atm pressure - equilibrium shifts right, yield increases - 450 - equilibrium shifts lefts, lower yield but MUCH faster reaction
catalyst - increases reaction rate
effect on equilibrium of increasing temperature
exothermic reaction
equilibrium shifts left, yield decreases
endothermic reaction
equilibrium shifts right , yield increases
effect on equilibrium of decreasing temperature
exothermic reaction
equilibrium shifts right, yield increase
endothermic reaction
equilibrium shifts left, yield decreases
effect on equilibrium of increasing gas pressure
equilibrium shifts to side with fewer gas molecules
effect on equilibrium of decreasing pressure
equilibrium sifts to side with more gas molecules
effect on equilibrium of increasing concentration
of products - equilibrium shifts left, yield decreases of reactants equilibrium shifts right , yield increases
effects on equilibrium of decreasing concentration
of products- equilibrium shifts right, yield increases of products - equilibrium shifts left , yield decreases
