Electrolysis + LCAs Flashcards
what does electrolysis mean
breaking down using electricity
name of the compund being broken by electrolysis
electrolyte
positive electrode
anode
negative electrode
cathode
why are electrodes often made of graphite
so that dont react with electrolyte or the products made
what happen during electrolysis
positively charged ions move to cathode and negative ions move to the anode
when can ionic compound be electrolysed
when molten or dissolved in water
OILRIS
oxidation is loss of e
reduction is gain of e
what happen in aqueous solutions
at the cathode the least reactive positive ion will gain e and be discharged
at anode if an halide is present it will be discharged if it not hydroxide will be dicharged
formula to discharhe hydroxide
4OH- =2H2O + O2 + 4e-
where do you get aluminium from
ore called bauxite
why is aluminium oxide mixd with molten cryolite
to lower high melting points
reducing energy required
formula for electrolysis of aluminium
2Al2O3 = 4Al+ 3O2
what doed oxygen react with
carbon anodes, making CO2
carbon anodes gradually burn away and need to be replaced regulary.
3 products of electrolysis of brine
chlorine gas (positive electrode)
H gas at cathode
sodium hydroxide solution is also formed
why sodium sulfate solution becomes more concnetrated during electrolysis
becasue H and hydroxide are removed, leving sodium sulfate in less water and therefre making it more concentrated
why is LCAs carried out
to assess the enviromental impact of products, processes or services
he enciromental impact are assesses in these stages
extracting and processing raw materials
manufacturing and packeging
use and operation during its lifetime
disposal at the end of its useful tiem
including transportation and energy consumption
why are LCAs results open to debate
assigning numerical values involves subjective judgements
