Unit B-2

thermodynamically unfavorable

negative E

thermodynamically favorable

positive E

five types of chemical reactions

double replacement, single replacement, combustion, synthesis, and decomposition

two types of double replacement reactions

precipitation and neutralization

chemical equation(s) that are never redox

double replacement

chemical equation(s) that are always redox

single replacement and combustion

chemical equation(s) that are sometimes redox

synthesis and decomposition

electrical potential / electromotive force / emf / E

driving force that makes voltaic/galvanic cells happen

E naught

E at standard conditions (1 atm, 1 M)

the metal in the reactant…

loses mass

the metal in the product…

gains mass

smaller molar mass means…

smaller changes in mass

anode

half-cell that is oxidizing

cathode

half-cell that is reducing

in a galvanic cell, electrons travel…

from anode to cathode

salt bridge

string draped across both half-cells that is usually made of a non-reacting/soluble salt like KNO₃ or NaNO₃

in the half-cell that loses mass…

atoms on the electrode separate into the solution as ions

in the half-cell that gains mass…

ions in the solution precipitate onto the electrode

when using a reduction half-reaction table, the oxidizing equation is…

the one with the lowest E naught

why shouldn’t we worry about stoichiometry when calculating the voltage of an electrochemical reaction?

standard potentials are intensive because E naught measures the potential energy difference per electrical charge

batteries “go dead” when…

the concentration of the reactants becomes too low and the concentration of the products becomes too high, meaning equilibrium is reached

Q quotient

Q = [products]^x / [reactants]^y

if Q is greater than 1…

the reaction is further along, and ln is positive

if Q is less than 1…

the reaction is not far along, and ln is negative

a positive ln means…

a smaller voltage

a negative ln means…

a larger voltage

substances that never end up in the Q quotient

pure liquids (l) and pure solids (s)

disproportionation reaction

reaction in which the same element is both oxidized and reduced

metallic properties

metal atoms are aligned in a regular and repeating pattern, outermost electrons can wander freely throughout, they have low ionization energies and a shiny luster, and they are easily oxidized, malleable, and ductile

why are metals good conductors of electricity?

electrons move easily in response to the electrical field

why are metals good conductors of heat?

free electrons can transmit kinetic energy

the determining factor in conductivity is…

delocalized electrons (electrons free to move)

conductivity of ionic compounds

do not conduct electricity as solids, but do conduct electricity when molten or dissolved