UNIT SEVEN Flashcards
thermodynamics
every chemical reaction accounted for by change in energy
thermochemistry
study of changes in heat energy that accompany chemical reactions and physical changes
heat
total of kinetic energies of particles in sample of matter
temperature
measure of average kinetic energy of particles in sample of matter (measured in joules, (kg/m^2)/s^2
heat transfer
when collisions between particles result in transfer of energy
thermodynamic equilibrium
average kinetic energy and temperature is the same
calorimetry
study of the transfer of heat
calorimeter
device that measures heat absorbed/released in chemical/physical change
3 processes of changing energy
- Heating/cooling
- Phase transitions
- Chemical reactions
heat of reaction
quantity of heat released/absorbed during chemical reaction
q=mCpAT
specific heat (Cp)
amount of energy required to raise temperature of 1 g by 1C
bond enthalpies
bonds formed/broken during reaction cause change in system potential energy; average energy needed to break all bonds estimated by adding average bond energies of all bonds in reactants (reactants-products)
Hess’s Law
overall enthalpy change in reaction equal to sum of enthalpy changes for individual steps
endothermic
when energy of system increases; energy gained from surroundings
exothermic
when energy of systems decreased; energy lost gained by surroundings
entropy (s)
degree of randomness in a system (higher entropy=higher disorder)
Gibbs Free Energy
maximum amount of non-expansion work that can be extracted from thermodynamically closed system
chemical kinetics
studies reaction rates and reaction mechanisms
differential rate law
expresses rate dependent on concentration
rate determining step
slowest elementary step
catalyst
increases reaction rates
chemical equilibrium
opposing processes occur at the same time and rate
reversible reaction
chemical reaction where products react to reform reactant
reversible chemical reaction
chemical equilibrium when rate of forward reaction equals rate of reverse reaction
buffered solution
resists change in pH, weak acid and salt of the weak acid
solubility constant
product of molar concentration of ions in saturated solution, each raised to power that is coefficient of that ion in the chemical equation
LeChatelier’s principle
if system at equilibrium is subjected to stress, equilibrium shifted in stress-relieving direction
common-ion effect
when addition of common ion brings precipitation/reduced ionization
