electrochemical cells

Question 1

what is an electrode

Answer 1

• solid electrical conductor
• there are two found in an electric cell

Question 2

what is an electrolyte

Answer 2

• aqueous electrical conductor
• 1 found in an electric cell

Question 3

what is the electric potential difference?

Answer 3

• the energy difference per unit charge
• measured in volts by voltmeter, also called voltage

Question 4

what is electric current

Answer 4

• 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)

Question 5

SI Unit: charge

Answer 5

sym = Q, unit = coulomb (C)

Question 6

SI Unit: current
(and conversion factor)

Answer 6

sym = I, unit= amperes, ammeter (A)
* 1 A = 1C/s

Question 7

SI Unit: potential difference
(and conversion factor)

Answer 7

sym = V, unit= volts: voltmeter (V)
*1 V = 1J/C

Question 8

SI Unit: Power
(and conversion factor)

Answer 8

sym= P, unit= watts, (W)
*1 W = 1J/s

Question 9

SI Unit: energy density

Answer 9

no sym, unit= joules per kilogram (J/kg)

Question 10

what is a primary cell?

Answer 10

a cell that cannot be recharged

Question 11

basic cells and uses of primary cells

Answer 11

dry cell (1.5V): consumer items
alkaline dry cell (1.5V): consumer items
mercury cell (1.35V): hearing aids, watches

Question 12

what is a secondary cell?

Answer 12

a cell that can be recharged by using electricity to reverse the reaction that occurs when the cell makes electricity itself

Question 13

basic cells and uses of secondary cells

Answer 13

Ni-Cd cell (1.25V): consumer + power items
Lead-acid cell (2V): large currents, vehicles

Question 14

what is a fuel cell?

Answer 14

cell which produces electricity through the reaction with fuel, can be used forever

Question 15

basic cells and uses of fuel cells

Answer 15

hydrogen-oxygen cell (1.2V): vehicles and space shuttles
aluminium-air cell (2V): electric cars

Question 16

what is a porous boundary?

Answer 16

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

Question 17

what is a half cell?

Answer 17

one half of a voltaic cell split by the porous boundary, consists of one electrolyte and one electrode

Question 18

what is a voltaic cell

Answer 18

• (galvanic cell)
• two half cells separated by a porous boundary with solid electrodes connected by an external circuit

Question 19

what is a cathode

Answer 19

• positive electrode in voltaic
• negative electrode in electrolytic
• where reduction occurs
• soa undergoes a reduction here

Question 20

what is an anode

Answer 20

• negative electrode in a voltaic cell
• positive electrode in an electrolytic cell
• where oxidation occurs
• sra undergoes oxidation at anode

Question 21

what is an inert electrode?

Answer 21

• unreactive electrode
• provide location to connect a wire and a surface to where a half-reaction can occur

Question 22

what is a salt-bridge?

Answer 22

U-shaped tube containing an inert electrode, connects the two half-cells in a voltaic cell

Question 23

what is standard cell?

Answer 23

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.

Question 24

what is the standard cell potential?
+formula

Answer 24

the maximum electric potential difference (V) of the cell operating under standard conditions.
Eºcell = Eºr (cathode) - Eºr (anode)

Question 25

what is the standard reduction potential?

Answer 25

represents the ability of a standard half-cell to attract electrons, thus undergo a reaction

Question 26

what is a reference half-cell?

Answer 26

a half-cell chosen as a reference and arbitrarily assigned an electrode potential of exactly zero volts; a standard hydrogen electrode

Question 27

what is corrosion?

Answer 27

electrochemical process in which a metal reacts with substances in the environment, returning the metal to an ore-like state.

Question 28

what does the rusting of iron require?

Answer 28

the presence of oxygen and water, accelerated by the presence of acidic solutions, electrolytes, mechanical stress, and contact with less active metals

Question 29

what is cathodic protection?

Answer 29

prevents corrosion of iron, iron is forced to become the cathode by supplying the iron with electrons using an impressed current or sacrificial anode

Question 30

what is an electrolytic cell?

Answer 30

cell with a nonspontaneous reaction, consists of two electrodes, an electrolyte, and an external battery or power source, uses electrolysis

Question 31

what is electrolysis?

Answer 31

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

Question 32

what happens during molten-salt electrolysis?

Answer 32

metal cations are reduced to metal atoms at the cathode, nonmetal anions are oxidized at the anode

Question 33

what is electrorefining?

Answer 33

a process used to obtain high-grade metals at the cathode from an impure metal at the anode

Question 34

what is electroplating?

Answer 34

a process in which a metal is deposited on the surface of an object placed at the cathode of an electrolytic cell

Question 35

what is faraday’s law?

Answer 35

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

Question 36

what is the faraday constant?

Answer 36

F, the quantity of charge transferred for every mole of electrons that flow in the cell, 9.65 x 10^4 C/mol e-

Question 37

what is the chloride anomaly?

Answer 37

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.