ACS PHYSICAL CHEMISTRY
THERMOCHEMISTRY PRACTICE PAPER 2026
MASTERED QUESTION SERIES
◉ What is the relationship between ΔS of a system, q, and T?
Answer: ΔS(system)=qrev/T
◉ What happens to entropy ΔS when temperature increases?
Answer: It increases
◉ What is the relationship between mass and entropy ΔS? Answer:
As mass increases, entropy increases
◉ What is the relationship between molecular complexity and
entropy ΔS? Answer: As molecular complexity increases, entropy
increases
◉ What is the relationship between ΔG and Q? Answer: ΔG=RTlnQ
◉ What happens to K as ΔG becomes more positive? Answer: It gets
smaller
,◉ What happens to K as ΔG becomes more negative? Answer: It gets
bigger
◉ What direction does a reaction proceed if ln Q/K is positive?
Answer: Reaction proceeds to the left/reactants
◉ What direction does a reaction proceed if ln Q/K is negative?
Answer: Reaction proceeds to the right/products
◉ Extensive Property Answer: property which is directly
proportional to the size of the system (i.e.. V, m, E )
◉ Intensive Property Answer: property which does not depend on
the size of the system (i.e. P, T, density, molar volume)
◉ van der Waals constants Answer: a reflects how strong the
molecules attract each other (IM forces); b reflects the size of the
molecule
--- van der Waals equation extends beyond the ideal gas law to take
into account attractive and repulsive forces
◉ Isotherm Answer: plot of P as a function of molar volume at
constant temperature
,◉ Law of Corresponding States Answer: Law which states "all gases
have the same properties of they are compared at corresponding
conditions"
◉ Boyle Temperature Answer: temperature at which repulsive and
attractive interactions cancel and the gas appears to behave ideally
◉ Heat (q) Answer: the manner of energy transfer that results from
temperature difference between system and surroundings
("unorganized motion")
◉ Work (w) Answer: the transfer of energy between system and
surroundings as a result of existence of unbalanced forces between
the two ("organized motion")
◉ State Function Answer: property that depends on the state of the
system, and not upon the history of the system (i.e. energy, entropy)
◉ Reversible Process Answer: when pressure the pressure exerted
on the system and the pressure of the system differ only
infinitesimally so slight changes are able to be made
◉ Path Function Answer: property that depends on the path taken
to reach the state of the system
, ◉ Adiabatic Process Answer: process which no energy as heat is
transferred (dq = 0 ; therefore, dU=dw )
◉ Enthalpy (H) Answer: total heat content of a system; it is
equivalent to the internal energy plus the products of pressure and
volume
◉ Heat of Combustion Answer: the heat involved in a combustion
reaction
--chemical reactions that absorb heat ( dH > 0) are called
endothermic
--chemical reactions that release heat (dH <0) are called exothermic
◉ Entropy (S) Answer: unavailability of a system's thermal energy
for conversion into mechanical work, often interpreted as the degree
of disorder or randomness in the system
---dS=0 for cyclic processes or reversible processes in isolated
system
---dS > 0 for spontaneous processes in isolated systems
◉ Helmoltz Energy (A) Answer: = U - TS
---will decrease during any spontaneous process that occur at
constant T and V and will achieve its minimum value at equilibrium
THERMOCHEMISTRY PRACTICE PAPER 2026
MASTERED QUESTION SERIES
◉ What is the relationship between ΔS of a system, q, and T?
Answer: ΔS(system)=qrev/T
◉ What happens to entropy ΔS when temperature increases?
Answer: It increases
◉ What is the relationship between mass and entropy ΔS? Answer:
As mass increases, entropy increases
◉ What is the relationship between molecular complexity and
entropy ΔS? Answer: As molecular complexity increases, entropy
increases
◉ What is the relationship between ΔG and Q? Answer: ΔG=RTlnQ
◉ What happens to K as ΔG becomes more positive? Answer: It gets
smaller
,◉ What happens to K as ΔG becomes more negative? Answer: It gets
bigger
◉ What direction does a reaction proceed if ln Q/K is positive?
Answer: Reaction proceeds to the left/reactants
◉ What direction does a reaction proceed if ln Q/K is negative?
Answer: Reaction proceeds to the right/products
◉ Extensive Property Answer: property which is directly
proportional to the size of the system (i.e.. V, m, E )
◉ Intensive Property Answer: property which does not depend on
the size of the system (i.e. P, T, density, molar volume)
◉ van der Waals constants Answer: a reflects how strong the
molecules attract each other (IM forces); b reflects the size of the
molecule
--- van der Waals equation extends beyond the ideal gas law to take
into account attractive and repulsive forces
◉ Isotherm Answer: plot of P as a function of molar volume at
constant temperature
,◉ Law of Corresponding States Answer: Law which states "all gases
have the same properties of they are compared at corresponding
conditions"
◉ Boyle Temperature Answer: temperature at which repulsive and
attractive interactions cancel and the gas appears to behave ideally
◉ Heat (q) Answer: the manner of energy transfer that results from
temperature difference between system and surroundings
("unorganized motion")
◉ Work (w) Answer: the transfer of energy between system and
surroundings as a result of existence of unbalanced forces between
the two ("organized motion")
◉ State Function Answer: property that depends on the state of the
system, and not upon the history of the system (i.e. energy, entropy)
◉ Reversible Process Answer: when pressure the pressure exerted
on the system and the pressure of the system differ only
infinitesimally so slight changes are able to be made
◉ Path Function Answer: property that depends on the path taken
to reach the state of the system
, ◉ Adiabatic Process Answer: process which no energy as heat is
transferred (dq = 0 ; therefore, dU=dw )
◉ Enthalpy (H) Answer: total heat content of a system; it is
equivalent to the internal energy plus the products of pressure and
volume
◉ Heat of Combustion Answer: the heat involved in a combustion
reaction
--chemical reactions that absorb heat ( dH > 0) are called
endothermic
--chemical reactions that release heat (dH <0) are called exothermic
◉ Entropy (S) Answer: unavailability of a system's thermal energy
for conversion into mechanical work, often interpreted as the degree
of disorder or randomness in the system
---dS=0 for cyclic processes or reversible processes in isolated
system
---dS > 0 for spontaneous processes in isolated systems
◉ Helmoltz Energy (A) Answer: = U - TS
---will decrease during any spontaneous process that occur at
constant T and V and will achieve its minimum value at equilibrium
