CHEM 210 Exam 2 Questions and Answers Latest Update 2025 Graded A+
Thermodynamics - Answers study of relationships between energy and work associated with chemical
and physical processes
A ___ of a system occurs under specific conditions without input energy - Answers spontaneous change
-occurs without added energy
-water flowing downhill
-if a change is spontaneous in one direction, it is not spontaneous in the other
-spontaneous does not mean instantaneous and does not give an indication of how long the process will
take (diamond to graphite)
-may be exothermic (-∆H) or endothermic (+∆H) (the sign itself does not by itself predict the direction of
a spontaneous change)
A ___ requires a continuous supply of energy to the system - Answers nonspontaneous change
-requires energy to be continually put into the system
-water flowing uphill (has to be pumped)
-irreversible without putting in work
First law of thermodynamics and spontaneity - Answers Law of conservation of energy - the total energy
of the universe is constant
∆Esys = -∆Esurr
-does not allow us to predict the direction of a spontaneous change
-tells us that energy of the universe is constant
-energy is transformed but never created or destroyed within a system
Spontaneous exothermic rxns - Answers freezing and condensing processes at certain conditions,
combustion rxns, oxidation of iron, formation of ionic compounds
Spontaneous endothermic rxns - Answers melting and vaporization processes at certain conditions,
dissolving of salts
Entropy (S) and the freedom of motion of particles - Answers solid->liquid->gas increases S
-a change in the freedom of motion of particles in a system affects the direction of a spontaneous
process
, ∆Ssys = Sfinal - Sinitial
-all spontaneous endothermic processes exhibit an increase in entropy
-motion is severely restricted in a solid, so it has a low entropy (freedom of motion of particels)
-liquid has slightly more freesom to move around
-gas has highest entropy
-spontaneous rxns result in a change that allows for the particles to have a wider range of energy of
motion
-entropy is a state function: depends only on the present state of the system and not on how it arrived
at that state, so the change in entropy of a system depends only on the entropy of its final and initial
states (path does not matter, only destination)
The number of ___ in a system is related to the entropy (S: units are J/K) of the system - Answers
microstates (W) - specific energetic configuration of system at given instant
S = k lnW
-k is Boltzmann constant: 1.38 x 10^-23 J/K
The number of microstates in a system is related to its entropy via equation - Answers -recall electrons
in an atom in certain energy levels: energy of an atom is quantized, molecules move around in the rxn
vessel. They rotate, vibrate, translate, and collide with other molecules. If you were to freeze the rxn at
any point, the distribution of energies of each particle represents a microstate (a specific configuration
of the system at an instant, location and energies of atoms or molecules
Quantitative meaning of an entropy change - Answers 1) Based on the number of microstates (W)
possible for a system
2) Based on changes in heat (q)
∆Ssys = (q rev) / T : rev is a reversible process
Entropy and the second law of thermodynamics - Answers all real processes occur spontaneously in the
direction that increases the entropy of the universe
∆Suniv = ∆Ssys + ∆Ssurr
∆Suniv > 0 for processes to be spontaneous
∆Ssurr = qsurr / T
∆Suniv = ∆Ssys + qsurr / T
Thermodynamics - Answers study of relationships between energy and work associated with chemical
and physical processes
A ___ of a system occurs under specific conditions without input energy - Answers spontaneous change
-occurs without added energy
-water flowing downhill
-if a change is spontaneous in one direction, it is not spontaneous in the other
-spontaneous does not mean instantaneous and does not give an indication of how long the process will
take (diamond to graphite)
-may be exothermic (-∆H) or endothermic (+∆H) (the sign itself does not by itself predict the direction of
a spontaneous change)
A ___ requires a continuous supply of energy to the system - Answers nonspontaneous change
-requires energy to be continually put into the system
-water flowing uphill (has to be pumped)
-irreversible without putting in work
First law of thermodynamics and spontaneity - Answers Law of conservation of energy - the total energy
of the universe is constant
∆Esys = -∆Esurr
-does not allow us to predict the direction of a spontaneous change
-tells us that energy of the universe is constant
-energy is transformed but never created or destroyed within a system
Spontaneous exothermic rxns - Answers freezing and condensing processes at certain conditions,
combustion rxns, oxidation of iron, formation of ionic compounds
Spontaneous endothermic rxns - Answers melting and vaporization processes at certain conditions,
dissolving of salts
Entropy (S) and the freedom of motion of particles - Answers solid->liquid->gas increases S
-a change in the freedom of motion of particles in a system affects the direction of a spontaneous
process
, ∆Ssys = Sfinal - Sinitial
-all spontaneous endothermic processes exhibit an increase in entropy
-motion is severely restricted in a solid, so it has a low entropy (freedom of motion of particels)
-liquid has slightly more freesom to move around
-gas has highest entropy
-spontaneous rxns result in a change that allows for the particles to have a wider range of energy of
motion
-entropy is a state function: depends only on the present state of the system and not on how it arrived
at that state, so the change in entropy of a system depends only on the entropy of its final and initial
states (path does not matter, only destination)
The number of ___ in a system is related to the entropy (S: units are J/K) of the system - Answers
microstates (W) - specific energetic configuration of system at given instant
S = k lnW
-k is Boltzmann constant: 1.38 x 10^-23 J/K
The number of microstates in a system is related to its entropy via equation - Answers -recall electrons
in an atom in certain energy levels: energy of an atom is quantized, molecules move around in the rxn
vessel. They rotate, vibrate, translate, and collide with other molecules. If you were to freeze the rxn at
any point, the distribution of energies of each particle represents a microstate (a specific configuration
of the system at an instant, location and energies of atoms or molecules
Quantitative meaning of an entropy change - Answers 1) Based on the number of microstates (W)
possible for a system
2) Based on changes in heat (q)
∆Ssys = (q rev) / T : rev is a reversible process
Entropy and the second law of thermodynamics - Answers all real processes occur spontaneously in the
direction that increases the entropy of the universe
∆Suniv = ∆Ssys + ∆Ssurr
∆Suniv > 0 for processes to be spontaneous
∆Ssurr = qsurr / T
∆Suniv = ∆Ssys + qsurr / T
