AP Chemistry Thermodyanmics

AP Chemistry Thermodyanmics

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Section 1

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Gibbs free energy

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Cards (51)

Section 1

(50 cards)

Gibbs free energy

Front

measure of spontaneity of process

Back

∆G°rx

Front

= ∑n∆G(f°products) - ∑n∆G°reactants

Back

particles

Front

in solution have higher entropy values than solids

Back

exothermic reaction

Front

reactants start higher than products

Back

-∆S

Front

becomes more ordered

Back

spontaneous endothermic reaction

Front

∆H > 0 ∆S > 0

Back

2nd Law of Thermodynamics

Front

process spontaneous in one direction can't be spontaneous in reverse direction

Back

entropy

Front

measure of disorder of system

Back

bomb calorimeter sealed, insulated container used for measuring the energy released during combustion

Front

sealed, insulated container used for measuring the energy released during combustion

Back

∆H

Front

H(products)-H(reactants)

Back

standard state conditions

Front

1. all gases are at 1 atm 2. all liquids are pure 3. all solids are pure 4. all solutions are at 1-M 5. the energy of formation of an element in its normal state is defined as 0 6. temperature used for standard state values is almost invariably room temperature. standard state values can be calculated for other temperatures, however.

Back

heat of formation

Front

∆H = ∑H(products)-∑H(reactants)

Back

heating curve

Front

a diagram that shows the temperature changes and changes of state of a substance as it is heated

Back

Enthalpy (heat) of combustion

Front

the heat released or absorbed (enthalpy change) during the formation of a pure substance from its elements, at constant pressure and usually denoted by ΔHf.

Back

heat of vaporization

Front

energy given off when substance condenses

Back

Entropy of a system increases when

Front

gases are formed from solids or liquids, liquids or solutions are formed from solids, the number of gas molecules changes during a chemical reaction

Back

2 moles of substance

Front

have higher entropy value than one mole

Back

what does Q stand for

Front

reaction quotient: the mass action expression at non-equilibrium conditions. the spontaneity of a reaction that has not reached equilibrium has to be measured in terms of ∆G which is not synonomous with ∆G° because the substances are not in standard state

Back

+∆G

Front

the forward process is nonspontaneous (the reverse is spontaneous)

Back

R (in thermo, not gases)

Front

8.31 J/mol*K

Back

∆G

Front

∆G° + RT(lnQ)

Back

+∆S

Front

becomes more random; disordered

Back

endothermic reaction

Front

reactants start lower than products

Back

∆G positive

Front

not spontaneous

Back

spontaneous at all temperatures

Front

-∆H (favorable) +∆H (favorable)

Back

∆G = 0

Front

reaction at equilibrium

Back

heat capacity

Front

heat ÷ ∆T

Back

energy released

Front

bonds formed; exothermic

Back

∆G negative

Front

spontaneous

Back

specific heat

Front

q = mc∆T

Back

addition of catalyst

Front

decreases activation energy only

Back

Exothermic Reactions

Front

negative ∆H, favors spontaneity but does not guarantee it.

Back

spontaneous at high T; non spontaneous at low T

Front

+∆H (unfavorable) +∆S (favorable)

Back

energy absorbed

Front

bonds broken; endothermic

Back

spontaneous at low T; nonspontaneous at high T

Front

-∆H (favorable) -∆S (unfavorable)

Back

Hess's law

Front

The overall enthalpy change in a reaction is equal to the sum of the enthalpy changes of the individual steps of the process.

Back

standard free energy

Front

∆G°(rxn) is the free energy change of a reaction when it occurs under standard conditions; when reactants in their standard states are converted to products in their standard states.

Back

1st Law of Thermodynamics

Front

energy of universe is constant

Back

spontaneous process

Front

one that proceeds on its own without assistance, they are irreversible unless the surroundings are changed and they can be fast or slow

Back

standard molar entropies of elements and diatomics

Front

are not 0 unlike standard molar enthalpies

Back

entropy change ∆S

Front

∑S°(products) - ∑S°(reactants)

Back

∆G°

Front

∆H - T∆S

Back

Finding ∆G when ∆G° and Q are known

Front

∆G = ∆G° + RTlnQ

Back

state function

Front

∆H, ∆S, ∆G

Back

-∆G

Front

the forward process is spontaneous (the reverse is nonspontaneous)

Back

Phase transitions

Front

if the process is melting, the ∆H is the same as the heat of fusion. if the process is freezing, the ∆H is the negative value of the heat of fusion. if the process is boiling, the ∆H is the heat of vaporization. if the process is condensing, the ∆H is the negative value of the heat of vaporization.

Back

nonspontaneous at all temperatures

Front

+∆H (unfavorable) -∆S (unfavorable)

Back

Calorimeter insulated device used for measuring the amount of heat absorbed or released through a chemical or physical process

Front

insulated device used for measuring the amount of heat absorbed or released through a chemical or physical process

Back

standard entropy

Front

S° is the absolute entropy of a mole of a substance at 1 atm and 35°C. J/Mol K. for all elements and compounds the standard entropy is always positive.

Back

heat of fusion

Front

energy taken in by substance when melts

Back

Section 2

(1 card)

potential energy diagram

Front

a diagram that shows the changes in potential energy that takes place during a chemical reaction

Back