chemistry paper 1 electrolysis Flashcards
define electrolysis and an electrolyte
electrical energy from a direct current supply, decomposes electrolytes.
an ionic compound that’s molten or dissolved in water
electrode…
a rod made of a metal or
graphite which carries the current
into or out of the electrolyte
cations are positive ions and are attracted to…
anions are negative ions and are attracted to..
the negative cathode
the positive anode
reduction takes place at the..
oxidation takes place at the…
negative cathode
positive anode
electrolysis of dissolved salts is carried out using …
metal produced at..
non-metal produced at…
when molten salt is electrolysed
electrolysis
cathode
anode
ions r discharged as atoms or molecules at the electrodes
what products r formed at the anode and cathode during the electrolysis of copper chloride?
cathode - Cu2+ and H+ ions. Cu ions discharged mre readily. Brown solid
anode - Cl- and OH- ions. Cl ions dishcarged mre readily, cl forms as Pale green gas
Cop Cl decomposes but h20 no change
what porducts r formed at the anode and cathode during the electrolysis of sodium chloride
cathode - Na+ and H+ ions. H+ discharged more readily than sodium. Hydrogen gas formed
anode - Cl- and OH- ions , Cl ions discharge more readily than hydroxide. CL forms pale green gas
sodium chloride decomposes to form hydrogen and clhorine. Na and OH- ions remain in solution
what porducts r formed at the anode and cathode during the electrolysis of sodium sulfate
cathode - Na+ and H+ ions. H+ ions discharged more readily. Hydrogen gas forms.
anode - sulfate ions & OH- . OH- ions discharged more readily
than sulfate
ions, so oxygen gas is formed.
overall, water decomposes to form hydrogen and oxygen
what porducts r formed at the anode and cathode during the water being acidified w sulfuric acid.
Cathode: H+ ions are attracted. Hydrogen ions discharged forming hydrogen gas
Anode: SO4 2- and OH- ions attracted. Hydroxide ioms discharged more readily. Oxygen gas formed
overall: water decomposes to form
hydrogen and oxygen:
2H2O(l) → 2H2(g) + O2(g
How can electrodes be used to purify copper using copper electrodes?
-copper atoms in in anode loose electrons to become copper ions
-these dissolve in the solution and migrate to cathode where they r deposited as pure copper
list the reactivity series
potas , sod, calc, mag, alum, Zn, Iron, copp silver gold
which metals from the RS react with cold water to form hydrogen and a metal hydroxide?
potass, sodium ,calc
which metals from the RS react slowly w cold water but react w steam to form hydrogen and a metal hydroxide
mag, allum, Zn , iron
which elements dont react w hot or cold water or dilute acid from RS?
copper silver and gold
which elements from the RS react violently with dilute acid?
potass and sodium
which elements from the RS react w dilute acid to form hydrogen and a salt solution?
calc, mag , allum, Zn , iron
the higher up the metal in the RS…
the easily it looses electrons
what is extraction?
whats an ore?
a process where a metal is obtained from its ore
an ore is a rock that contains enough of a compound to extract a metal
what method of extraction is used for potasssium to alumnium in the reactivity series?
electrolysis of a molten compound
what method extraction can be used for zinc to copper in the RS
heat an ore with carbon
what method of extraction can be used for silver and gold
non as its an uncombined element
define bioleaching (a form of metal extraction)
define phytoextraction
using bacteria to extract metal from their ores
using plants to extract metal from their ores. Plants are burnt to form ash from which the metal is extracted
adv and disadv of both bioleaching and phytoextraction
adv - no harmful gases produced, causes less damage to landscape than mining
very slow
adv and disadv of just bioleaching
doesnt require high temps
toxic substances produced, damage to environ
adv and disadv of just phytoextraction
can extract metals from contaminated soils
more expensive than mining some ores, growing plants depend on weather conditions
what is oxidation and reduction in terms of oxygen?
oxidation is the gain of oxygen and reduction as the
loss of oxygen
how do you obtain a metal from metal oxide cores?
oxygen is removed . Once removed the compound is said to be reduced
define corrosion and rusting
when a metal reacts with oxygen (becomes oxidised) making the metal weaker over time.
rusting - the corrosion of iron or steel. H20 or 02 must be present
why doesnt metals like aluminium rust?
their surfaces form a protective oxide layer which prevents further reaction
what are advantages of recycling metals?
disadv
-natural reserves of metal ores will last longer
-less waste metals end up in landfill sites
-costs and energy using in collecting transporting and sorting metals
what is a life cycle assessment and what are the 4 stages?
-its carried out to work out the environmental impact of a product and whether its worthwhile to manufacture and recycle the product
1. using the product
2. disposal of product
3. obtaining and processing raw materials
4. manufaturing and packaging the product
most metals = transition metals and their typical properties are….
a high melting point
b high density
c the formation of coloured compounds
d catalytic activity of the metals and their compounds
as exemplified by iron
what are reversible reactions? ⇌
dynamic equilibrium?
a reaction that works in both direction
when the forwards and backwards reactions in a reversible chem reaction are occuring at the same rate
what conditions are needed for the haber process?
a temperature 450 °C
b pressure 200 atmospheres
c iron catalyst
what is sacrificial protection
using a more reactive metal to prevent iron from rusting
how is the position of a dynamic equilibrium
affected
a temperature
b pressure
c concentration
describe the formation of ammonia
- reversible reaction
between nitrogen (extracted from the air) and hydrogen
(obtained from natural gas)
-it can reach a dynamic equilibrium
what is electroplating? whys it used
using electricity to coat one metal with a thin layer of another metal
to improve its appearance; to improve its
resistance to corrosion/rusting
define galvanising
coating iron or steel with a thin layer of zinc to improve its resistance to rusting
zinc improves corrosion resistance by stopping water reachin iron or steel (acting as a sacrificial metal)
Explain why converting pure metals into alloys
often increases the strength of the product
making it into an alloy adds extra atoms which distorts the regular structure so the atoms can no longer slide over each other as easily making it less malleable
what is an alloy
alloy steels are made by..
a mixture of metals
deliberately adding other elements to iron
stainless steels…
resist rusting. it contains chromium that reacts with o2 in the air, creating a layer of chromium oxide thick enough to stop air and water reaching metal below
how are aluminium copper and gold used
