electrolysis (topic 4) Flashcards
suggest one reason why spoons are electroplated (metal spoons coated with silver)
improve appearance
at the cathode (negative electrode) is it the most or least reactive of the two elements that will be produced
least reactive
what is the type of bond in a molecule of hydrogen chloride
covalent
- hydrogen chloride has a low boiling point
- hydrogen chloride is made of simple molecules
name a gas produced at the negative electrode
hydrogen
hydrogen is only produced at the cathode if the metal
if the metal is more reactive than hydrogen
name a gas produced at the positive electrode
oxygen
explain why aluminium ions move towards the negative electrode (2)
- aluminium ions are positive
- so are attracted (to the negative electrode)
c
atoms
- insoluble
- precipitation
name the product formed at the postitive electrode
chlorine
cryolite
what is used as a solvent for aluminium oxide
molten cryolite
explain why oxide ions (O2−) move to the positive electrode (2)
- oxide ions are negative
- so are attracted to the positive electrode
reacts with oxygen
(2)
- alloy atoms are not in layers
- so alloy layers cannot slide
- it is an opinion
- not enough reliable evidence
- may be other factors involved
a is
b is
c is
a is chlorine gas
b is hydrogen gas
c is sodium hydroxide solution
- the solution may not have been properly stirred
- the electrodes may have been a larger distance apart
- the drop of sodium chloride may have been a smaller volume
explain, in terms of bonding, why pure water does not conduct electricity (2)
- pure water is covalent / molecular (simple) or contains molecules
- therefore has no free electrons
explain why sodium chloride solution conducts electricity (2)
- because there are ions in sodium chloride
- which can move or carry the current / charge
- copper / ores are running out / harder to find
- there are very small amounts of high-grade copper ores left
- copper metal is in demand
- copper is expensive
- large amounts
- waste rock takes up a lot of space
the reaction in the furnace could cause environmental pollution, explain how
- (copper sulfide reacts with oxygen to) produce sulfur dioxide
- that causes acid rain
the extraction of pure copper is expensive, give one reason why
- large amounts of fuels / energy used (for the furnace and electrolysis)
- (the extraction has) many steps / stages / processes
- large amounts of ore / material have to be mined
pure copper is produced by electrolysis of copper sulfate solution, which electrode do the copper ions move towards, give a reason for your answer
- the negative electrode / cathode
- because copper ions / Cu^2+ are positively charged
what is used in phytomining to remove copper compounds from the land
plants
solution X is alkaline, which ion makes solution X alkaline
- hydroxide / OH^–
- hydrogen / H+
(1)
low percentage / very little of metal (in the ore)
has melting point lower than 950°C
(2)
- electrode made of carbon
- oxygen reacts with electrode