ch 18 quiz
The free energy of formation of pure elements in their standard states is
0
standard state of solution
1 M
standard state of gas
1 atm
standard state of solid or liquid
1 atm ast 25c
spontaneous processes that proceed from a system of lower potential energy to a system at higher potential energy.
endothermic
first law of thermodynamics
energy cannot be created or destroyed
ΔE = q + w ΔE = ΔH + PΔV
energy conservation equation
what do non spontaneous processes require
energy input
two factors that determine whether a reaction is spontaneous
enthalpy change entropy change
larger, more complex molecules have larger
entropy
the larger the molar mass, the larger the
entropy
For a process where the final condition is more orderly than the initial condition, ΔSsystem is _____ and
entropy change is unfavorable for the process to be spontaneous.
When ΔG = 0 the reaction is at
equilibrium
A reaction is generally ______ if the bonds in the products are stronger than the bonds in the reactants.
exothermic
The entropy increase must come from heat released by the system; the process must be
exothermic
Solids have ___ macrostates than liquids, which have ____. macrostates than gases.
fewer, fewer
The ____ the original temperature, the less effect addition or removal of heat has.
higher
Most spontaneous processes proceed from a system of _____ potential energy to a system at _____ potential energy.
higher, lower (exothermic)
when is the reaction thermodynamically favorable
if system after reaction has less potential energy than before the reaction
If the entropy of the system decreases, then the entropy of the surroundings must ____ by a larger amount.
increase
When a system process is exothermic, it adds heat to the surroundings, _____ the entropy of the surroundings
increasing
exothermic reaction, where does the heat from the SYSTEM go
into the surroundings
ΔSuniv > 0
irreversible process
If the reaction achieves its theoretical limit
it is a reversible reaction
ΔH is positive when
it is endothermic
ΔH is negative when
it is exothermic
The amount the entropy of the surroundings changes depends on
its original temperature
ΔH is measured in
kj/mol
dissolved solids have
larger entropy
the less constrained the structure of an allotrope is, the
larger its entropy
every energy transition results in ___ of energy
loss
fewer steps in heat tax results in
lower total heat tax
the more degrees of freedom the molecules have, the
more macrostates are possible.
ΔG is negative or positive when spontaneous
negative
When heat is added to surroundings that are cool it has more of an effect on the entropy than it would have if the surroundings were already hot.
true
spontaneity does not equal fast or slow
true
when does g=g
when reactants and products are in their standard states
what does thermodynamics predict
whether a process will occur under the given conditions
absolute entropy of substances is always
positive
For a process where the final condition is more random than the initial condition, ΔSsystem is____ and the
positive entropy change is favorable for the process to be spontaneous.
what system require less energy than ordered systems.
random system
Entropy change is favorable when the result is a more
random system. delta s is positive
changes that increase entropy
reactions whose products are in a more random state reactions with larger numbers of product molecules than reactant molecules increase in temperature solids dissociating into ions upon dissolving
If a reaction is reversed, the sign of its ΔG value
reverses
ΔSuniv = 0
reversible process
ΔSuniverse = ΔSsystem + ΔSsurroundings
second law of thermodynamics
real reaction are irreversible because
some of the free energy is lost as heat
A reaction is generally _______ if the bonds in the products are weaker than the bonds in the reactants.
endothermic
ΔGsys = ΔHsys−TΔSsys
Gibbs free energy
ΔG will be positive when
delta h is postive and delta s is negative
qsurroundings = −qsystem
The entropy change in the surroundings is proportional to the amount of heat gained or lost.
Entropy
a thermodynamic function that increases as the number of energetically equivalent ways of arranging the components increases, S.
absolute entropy of a substance
amount of energy it has due to dispersion of energy through its particles
reversible process
at equilibrium results in no change of free energy
why aren't spontaneous processes reversible
because of the net release of energy when it proceeds in that direction only goes in one direction
why do spontaneous processes occur
because they release energy from the system
ΔS = Sfinal − Sinitial
changes in entropy
how is spontaneity determined
comparing chemical potential energy of system before reaction to free energy of the system after the reaction
how do you determine the direction of spontaneity
comparing potential energy of system at start and end
two ways energy is lost from a system
converted to heat, q used to do work, w
The entropy change in the surroundings is also inversely proportional to its
temperature
free energy of formation
the change in free energy when 1 mol of a compound forms from its constituent elements in their standard states.
standard entropy change
the difference in absolute entropy between the reactants and products under standard conditions.
entropy change, ΔS
the difference in randomness of the reactants compared to the products
enthalpy change, ΔH,
the difference in the sum of the internal energy and PV work energy of the reactants to the products.
The macrostate with the highest entropy also has
the greatest dispersal of energy
Gibbs free energy
the maximum amount of work energy that can be released to the surroundings by a system for a constant temperature and pressure system.
The free energy
the maximum amount of energy released from a system that is available to do work on the surroundings
spontaneous process
the process that will occur under conditions
standard state
the state of a material at a defined set of conditions
second law of thermodynamics
the total entropy change of the universe must be positive for a process to be spontaneous.
If a process is spontaneous in one direction, it must be nonspontaneous in the opposite direction.
true
The enthalpy change is favorable for exothermic reactions and unfavorable for endothermic reactions.
true
When K = 1
ΔGº is 0 and the reaction is at equilibrium under standard conditions.
When K > 1
ΔGº is negative and the reaction is spontaneous in the forward direction under standard conditions
When K < 1
ΔGº is positive and the reaction is spontaneous in the reverse direction under standard conditions
ΔG will be negative when
ΔH is negative and ΔS is positive. Exothermic and more random ΔH is negative and large and ΔS is negative but small. ΔH is positive but small and ΔS is positive and large. high temperature