AP®︎ Chemistry: Topic 9.10 Flashcards

298 K, 1 atm, 1 M dissolved species, and reaction quotient Q = 1.

Any cell conditions where concentrations, pressures, temperature, or Q differ from standard values.

E°cell is the voltage at standard conditions; Ecell is the actual voltage under current conditions.

Q is products over reactants using activities or concentrations, omitting pure solids and liquids.

Q = 1 at standard conditions; Q < 1 means reactant-favored; Q > 1 means product-favored.

Voltage measures the tendency for a redox reaction to proceed until equilibrium is reached.

The farther a system is from equilibrium, the larger the absolute value of its voltage.

If Q < 1, Ecell > E°cell; if Q > 1, Ecell < E°cell; if Q = 1, Ecell = E°cell.

Changes moving Q toward K lower |Ecell|, while changes moving Q away from K raise |Ecell|.

Changing ion concentrations changes Q, which changes the cell voltage under nonstandard conditions.

Their activities are treated as 1, so they are omitted from the reaction quotient.

Changing the amount or surface area of a pure solid electrode does not change Q or voltage.

Electrons flow from the lower-ion-concentration half-cell toward the higher-ion-concentration half-cell to equalize concentrations.

Substituting equilibrium conditions gives Ecell = 0 and connects standard voltage to the equilibrium constant.

A functioning electrochemical cell is not at equilibrium, so Le Châtelier’s principle does not apply.

At equilibrium, Q equals K and the cell potential is zero.

It relates cell potential to Q, letting you predict voltage changes qualitatively under nonstandard conditions.