Ch 3 - RR, GC, Eo Flashcards
A galvanic cell
is a type of electrochemical cell that converts chemical energy into electrical energy.
An electrochemical cell is a
device that converts chemical energy into electrical energy, or vice versa
A salt bridge is an
electrical connection between two half-cells
in a galvanic cell;
usually made from a material saturated
in electrolyte solution.
A battery is a
combination of cells connected in series,
A primary cell is a
galvanic cell that cannot be recharged.
describe galvanic cell
- composed of two half-cells connected by a
salt bridge. - Each half-cell contains an electrode in contact with
a solution.
(one half-cell might contain Cu(s) and
Cu2+(aq), the other might contain Zn(s) and Zn2+(aq).)
species present in each half-cell form a conjugate redox pair
salt bridge is made from an absorbent material such as filter paper saturated in an electrolyte solution such as potassium nitrate solution.
potential diff in the context of gcells
measures the tendency to push electrons into the external circuit.
electromotive force between two points in a
circuit.
The standard electrode potential measured by
or standard
reduction potential (E°) of a half-cell is measured by
connecting the half-cell to a standard hydrogen halfcell and measuring the voltage produced.
hydrogen half cell
used as the standard
reference half-cell; its value is arbitrarily assigned
as zero.
current flows in GC bcz one half C
has a greater tendency to push electrons into the cricuit - causes potential diff to exist between the 2 cells
standard conditions
100kPa 1M concentration of solutions E0 25 degrees
The standard electrode potential gives a
numerical measure of the tendency of a half-cell reaction to occur as a reduction reaction. (0.44 V is standard)
electrochemical series,
top left of the series
bottom right
strongest oxidising agent
(with the most positive
E° value)
the strongest reducing agent (with the most negative E° value).
When reactants react in a galvanic cell, ___
energy is transformed into ____ energy.
However, when they react directly, their
energy is transformed into ___ energy.
chemical, electrical
chemical, heat
cell potential diff is calculated by
E0 [cathode, higher value, OA half cell] - E0 [ anode, lower value, RA half cell]
stronger reducing agent
- negative/positive
electrode.
The stronger oxidising agent
- negative/positive electrode.
anode - negative
cathode - positive
Describe how the standard electrode potential (E°)
of a half-cell is measured using a standard hydrogen
electrode. In your answer, describe how the sign of the electrode potential is determined.
half-cell constructed at standard conditions
(gas pressures of 100 kPa, concentrations of 1 mol L’1), 25°C.
- cell connected to a standard hydrogen electrode to form a galvanic cell.
- the potential difference of the cell is measured with a voltmeter.
This value is the standard electrode potential (E°). If the electrode in the halfcell is negative, the E° is given a negative sign; if the electrode in the half-cell is positive the E° is given a positive sign.
what does the E0 value tell us in terms of applications
negative = better at gaining electrons (reducing agent/ gonna get oxidised)
the higher the value is the stronger of an oxidising agent it is. so better at gaining electrons. that cell will undergo reduction.
Explain why predictions of reactions based on
the standard electrode potentials do not always
correspond to what may be observed when the
reactants are mixed
- When conditions are not standard, the order of half-reactions
in the electrochemical series may be different. - The rate of the reaction may be slow.
