Electrolytic cells Flashcards
electroylsis
involves the passage of electrical energy from a direct current (DC) power supply through a conducting liquid. supplies e- to make a chemical
what is the purpose of electricity in an electrolytic cell
it causes redox reactions that are normally non-spontaneous reactions to occur
structure of an electrolytic cell
usually takes place in one container as the chemicals will not spontaneously react, however products need to be seperated as otherwise they would spontaneously react with each other to re form the orgiginal reactants
electrode
a rod of metal or graphite through which an electric current flows into or out of an electrolyte
electrolyte
the ionic compound in a molten or dissolved solution that conducts electricity
anode in electrolytic cell
the positive electrode, still site of oxidation, with anions attracted to it
cathode in electrolytic cell
the negative electrode, still site of reduction, with cations attracted to it
where does the power supply go
the cathode, providing it with a supply of electrons, causing it to become negatively charged
where do the cations move
towards the cathode where they gain electrons (reduction)
where do the anions move
towards the anode, where they lose electrons (oxidation)
movement of electrons in electrolutic cell
they move from the anode back towards the power supply to be supplied to the cathode
what are the charge carriers in an electrolytic cell
electrons are the charge carriers in the external circuit, ions are the charge carriers in the electrolyte
trend in oxidant strength ECS
decreases down the series, strongest oxidant is on the top left
trend in reductant strength ECS
increases down the series, strongest reductant is on the bottom right
how do chemicals react based on strength of oxidants/reductants
the strongest oxidant will always react with the strongest reductant (true for both galvanic cells and electrolytic cells)
how to predict reactions from the electrochemical series for electolytic cells
oxidation reaction: occurs for the higher reaction, this higher reactions is reversed
reduction reaction: occurs for the lower reaction, this lower reaction stays the same (anticlockwise)
how to calculate E° of electrolytic cell
(E° of oxidant/lower equation) - (E° of reductant/higher equation)
+E°
spontaneous redox reactions
-E°
non-spontaneous redox reaction
molten meaning
when an ionic compound is heated above its melting point to become a liquid, no water is present
electrolysis of aqueous solutions
means that there is a solution of ions, hence water is present in the cell and may react
how to predict the half reactions in an aqueous electrolytic cell
the stronger oxidising agent and therefore the species that is more likely to be reduced appears higher on the chemical series. the stronger reducing agent appears lower in the chemical series and therefore is more likely to be oxidised is lower on the chemical series. Basically choose the half equations that are closest to each other on the ECS and therefore require the least amount of voltage
differences in galvanic cells and electrolytic cells
Galvanic: produces electricity, have spontaneous reactions, convert chemical energy to electrical energy, anode (-), cathode(+).
Electrolytic: consumes electricity, have non-spontaneous reactions, converts electrical energy to chemical energy, anode (+), cathode (-)
similarities in galvanic cells and electrolytic cells
reduction occurs at the cathode, oxidation occurs at the anode
