ch8: production of chemicals by electrolysis Flashcards
what sort of reaction is electrolysis
non-spontaneous (forced) reaction
what sort of energy conversion occurs in an electrolytic cell?
electrical energy is converted into chemical energy
what are the polarity of electrodes in electrolysis?
- anode is positive
- cathode is negative
similarities between galvanic and electrolytic cells
- oxidation always occurs at the anode
- reduction always occurs at the cathode
- electron flows from anode to cathode
- strongest oxidant will react with the strongest reductant
how to determine the non-spontaneous reaction from the electrochemical series?
smallest gap between oxidants and reductants
what is a molten liquid?
a molten liquid is formed when heat is applied to a solid to form a liquid. there is no water present in a molten liquid.
how can you tell which electrode is the positive and negative in an electrolytic cell?
the positive electrode will be connected to the positive terminal and the negative electrode will be connected to the negative terminal.
why do the products of an electrolytic cell have to be kept apart?
because they will react spontaneously.
differences between galvanic and electrolytic cells?
galvanic cells
- produce electricity
- react spontaneously
- chemical energy -> electrical energy
- anode is neg, cathode is pos
electrolytic cells
- consume electricity
- non-spontaneous reaction
- electrical energy -> chemical energy
- anode is pos, cathode is neg
faraday’s first law of electrolysis
Q=It
where Q is charge (coulombs)
I is current (amps)
t is time (seconds)
faraday’s second law of electrolysis
Q=n(e-)*F
where Q is charge(coulombs)
n(e-) is the moles of an electron
F is faraday’s constant (96500)
equation of the cathode when producing green hydrogen?
2H+(aq) + 2e -> H2(g)
equation of the anode when producing green hydrogen?
2H2O(g) -> O2(g) + 4H+(aq) + 4e
full equation of production of green hydrogen?
2H2O(g) -> O2(g) +H2(g)
energy conversion in a polymer electrolyte membrane (PEM) cell
electrical -> chemical
energy conversion in an artificial photosynthesis cell
sunlight/light energy -> chemical
what is the power source of a PEM cell in order for the production of green hydrogen to occur?
renewable energy (ie solar or wind-powered)
how is the electric charge in an artificial photosynthesis managed if electrons only flow in one direction?
- as electrons are being produced, cations are also being produced at the same time which balances out the charges.
- additionally the same proportion of electrons and cations are used up at the cathode so the charge inside the cell remains neutral.
