electrochemical cells Flashcards
what is an electrode
- solid electrical conductor
- there are two found in an electric cell
what is an electrolyte
- aqueous electrical conductor
- 1 found in an electric cell
what is the electric potential difference?
- the energy difference per unit charge
- measured in volts by voltmeter, also called voltage
what is electric current
- measure of the rate of flow of charge past a point in an electric circuit
- measured in amperes by ammeter
- expresses total charge transferred by movement of particles in coulombs (C)
SI Unit: charge
sym = Q, unit = coulomb (C)
SI Unit: current
(and conversion factor)
sym = I, unit= amperes, ammeter (A)
* 1 A = 1C/s
SI Unit: potential difference
(and conversion factor)
sym = V, unit= volts: voltmeter (V)
*1 V = 1J/C
SI Unit: Power
(and conversion factor)
sym= P, unit= watts, (W)
*1 W = 1J/s
SI Unit: energy density
no sym, unit= joules per kilogram (J/kg)
what is a primary cell?
a cell that cannot be recharged
basic cells and uses of primary cells
dry cell (1.5V): consumer items
alkaline dry cell (1.5V): consumer items
mercury cell (1.35V): hearing aids, watches
what is a secondary cell?
a cell that can be recharged by using electricity to reverse the reaction that occurs when the cell makes electricity itself
basic cells and uses of secondary cells
Ni-Cd cell (1.25V): consumer + power items
Lead-acid cell (2V): large currents, vehicles
what is a fuel cell?
cell which produces electricity through the reaction with fuel, can be used forever
basic cells and uses of fuel cells
hydrogen-oxygen cell (1.2V): vehicles and space shuttles
aluminium-air cell (2V): electric cars
what is a porous boundary?
separates the two electrolytes in a voltaic cell, at least for short time, while still permitting ions to move between the solution through tiny openings within them
what is a half cell?
one half of a voltaic cell split by the porous boundary, consists of one electrolyte and one electrode
what is a voltaic cell
- (galvanic cell)
- two half cells separated by a porous boundary with solid electrodes connected by an external circuit
what is a cathode
- positive electrode in voltaic
- negative electrode in electrolytic
- where reduction occurs
- soa undergoes a reduction here
what is an anode
- negative electrode in a voltaic cell
- positive electrode in an electrolytic cell
- where oxidation occurs
- sra undergoes oxidation at anode
what is an inert electrode?
- unreactive electrode
- provide location to connect a wire and a surface to where a half-reaction can occur
what is a salt-bridge?
U-shaped tube containing an inert electrode, connects the two half-cells in a voltaic cell
what is standard cell?
a voltaic cell in which each half-cell contains all the entities shown in the half-reaction equation at SATP conditions, with a concentration of 1.0 mol/L for the aqueous solutions.
what is the standard cell potential?
+formula
the maximum electric potential difference (V) of the cell operating under standard conditions.
Eºcell = Eºr (cathode) - Eºr (anode)
what is the standard reduction potential?
represents the ability of a standard half-cell to attract electrons, thus undergo a reaction
what is a reference half-cell?
a half-cell chosen as a reference and arbitrarily assigned an electrode potential of exactly zero volts; a standard hydrogen electrode
what is corrosion?
electrochemical process in which a metal reacts with substances in the environment, returning the metal to an ore-like state.
what does the rusting of iron require?
the presence of oxygen and water, accelerated by the presence of acidic solutions, electrolytes, mechanical stress, and contact with less active metals
what is cathodic protection?
prevents corrosion of iron, iron is forced to become the cathode by supplying the iron with electrons using an impressed current or sacrificial anode
what is an electrolytic cell?
cell with a nonspontaneous reaction, consists of two electrodes, an electrolyte, and an external battery or power source, uses electrolysis
what is electrolysis?
the process of supplying electrical energy to force a nonspontaneous reaction, uses external power to causes electron transfer within the electrolytic cell, reverse of spontaneous reaction
what happens during molten-salt electrolysis?
metal cations are reduced to metal atoms at the cathode, nonmetal anions are oxidized at the anode
what is electrorefining?
a process used to obtain high-grade metals at the cathode from an impure metal at the anode
what is electroplating?
a process in which a metal is deposited on the surface of an object placed at the cathode of an electrolytic cell
what is faraday’s law?
the mass of an element produced or consumed at an electrode is directly proportional to the time the cell operated - as long as the current is constant
what is the faraday constant?
F, the quantity of charge transferred for every mole of electrons that flow in the cell, 9.65 x 10^4 C/mol e-
what is the chloride anomaly?
when chloride and water are the only 2 reducing agents in a substance, chloride will act as the reducing agent, even though the redox table predicts water to be SRA.
