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