how does electric current flow?
 | Porous
barrier: any medium through which ions can slowly pass |
| Electricity:
energy associated with electrons that have moved from one place to another |
| Voltaic
cell: an electrochemical cell in which a spontaneous redox reaction produces
a flow of electrons through an external circuit |
| Circuit:
closed loop path for current to follow |
| Half-cell:
the part of a voltaic cell in which either oxidation or reduction occurs. It
consists of a single electrode immersed in a solution of its ions |
| Anode:
the electrode at which oxidation occurs as electron are lost by some
substance |
| Cathode:
the electrode at which reduction occurs as electrons are gained by some
substances |
| Oxidation:
loss of electrons by an atom or an algebraic increase in its oxidation state |
| Reduction:
the gain of electrons by an atom or the algebraic decrease in its oxidation
state |
| Redox
reaction: a chemical reaction involving oxidation and reduction |
| The flow of free electrons through a circuit produces electricity in a voltaic cell |
| An element loses electrons when it is oxidized and gains electrons when it is reduced |
how are electron transfers described?
| Oxidation
state: a numerical representation of an atom’s share of the bonding
electrons. In ionic compounds, it is the average charge assigned to an atom
according to electronegativities |
| Redox
reactions involve changes in oxidation states |
| Redox
equations may be balanced by separating the reaction into half-reactions,
balancing the half-reactions in terms of mass and charge, and then
recombining them |
| Both mass and charge are conserved in redox reactions |
how do batteries work?
| Battery:
single voltaic cell or group of voltaic cells that are connected together.
They also run on redox reactions |
| Electrolysis:
a process in which electric energy is used to bring out a chemical change |
| Electrolytic
cell: an electrochemical cell in which electric energy from an external
source causes a non-spontaneous redox reaction to occur |
| A
battery is “dead” when its component half-cells reach equilibrium with
each other |
| Electrolytic
cells are electrochemical cells in which electric energy is converted into
chemical energy. They are the opposite of voltaic cells |
| Applied
external current restores the half-cells of rechargeable batteries to their
original, unreacted states |