Chapter 16: Thermodynamics Flashcards
what is the first law of thermodynamics?
the total energy-mass of the universe is constant. however, this does not tell us anything about the direction of change in the universe
what happens when two objects of different temperatures come into contact?
heat spontaneously flows from the hotter object to the colder object
microstates
a specific configuration of all the locations and energies of atoms or molecules that make up a system. the number of microstates creates chaos
what happens to S when temperature changes?
S increases as temperatures rises
what happens to S when physical states and phase changes?
S increases as a more ordered phase changes to a less ordered phase
What happens to S in a dissolution of a solid or a liquid?
S of a dissolved solid or liquid is usually greater than the S of the pure solute, however, the extent depends upon the nature of the solute and solvent
What happens to S in a dissolution of a gas?
a gas becomes more ordered when it dissolves in a solid or liquid
what happens to S in atomic size or molecular complexity?
in similar substances, increased mass relate directly to entropy.
what is entropy?
the measure of the chaos or disorder in a system
entropy of a system
the entropy change that occurs when all reactants and products are in their standard states
formula for the entropy of a system
sum of products - sum of reactants
second law of thermodynamics
the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. isolated systems spontaneously evolve toward thermodynamic equilibrium, the state with maximum entropy
formula to know if a reaction is spontaneous
S - H/T
a positive value indicates it is spontaneous
Gibbs Energy
a spontaneous reaction occurs when the combination of the enthalpy (H) and the entropy (S) result in favorable conditions. the individual values of enthalpy and entropy are not enough to make this call which is where G exists
how is G fixed?
G is fixed at temperature and is usually calculated at 298 K
formula of G
G = H-TS
what is the reaction when S>0 (increase entropy), and H>0 (endothermic, increase enthalpy)?
G < 0 at high temps
G > 0 at low temps
process is spontaneous at high temps
what is the reaction when S>0 (increase entropy), and H<0 (exothermic, decrease enthalpy)?
G < 0 at any temp
process is spontaneous at any temperature
what is the reaction when S<0 (decrease entropy), and H<0 (exothermic, decrease enthalpy)?
G < 0 at low temps
G > 0 at high temps
process is spontaneous at low temps
what is the reaction when S<0 (decrease entropy), and H>0 (endothermic, increase enthalpy)?
G > 0 at any temp
process is nonspontaneous at any temperature
formula for the temperature in which a reaction is spontaneous
T = H/S
what happens if Q/K < 1?
then ln Q/K < 0, reaction proceeds to the right (G<0)
what happens if Q/K > 1?
then ln Q/K > 0, reaction proceeds to the left (G>0)
what happens if Q/K = 1?
then ln Q/K = 0, the reaction is at equilbrium (G=0)
formula for change in G
G = -RT ln K
