Ch. 7: Thermochemistry (Complete) Flashcards
defn: system
the matter that is being observed – the total amount of reactants and products in a chemical reaction
defn: surroundings (environment)
everything outside of that system
how do you determine where to place the boundary between system and surroundings?
it depends on what phenomenon one is studyign
defn + example: isolated system
the system cannot exchange energy (heat and work) or matter with the surroundings
example: insulated bomb calorimeter
defn + example: closed system
the system can exchange energy (heat and work) but not matter with the surroundings
example: steam radiator
defn + example: open system
the system can exchange both energy (heat and work) and matter with the surroundings
example: pot of boiling water
defn: process
when a system experiences a change in one or more of its properties (such as concentrations of reactants or products, temperature, or pressure)
defn + first law of thermodynamics: isothermal processes
how does this appear on a P-V graph?
occur when the system’s temperature is constant
so U is constant, so
delta U = 0 so,
first law of thermodynamics simplifies to Q = W (the heat added to the system equals the work done by the system)
on P-V graph: hyperbolic
if the temperature of the system is constant, what does this imply about the total internal energy of the system?
the total internal energy of the system (U) is also constant throughout the process
defn + first law of thermodynamics: adiabatic processes
how does this appear on a P-V graph?
no heat is exchanged between the system and the environment
so the thermal energy of the system is constant throughout the process
when Q = 0, first law is delta U = - W (the change in internal energy of the system is equal to work done on the system)
on P-V graph: hyperbolic
defn + first law of thermodynamics: isobaric processes
how does this appear on a P-V graph?
occur when the pressure of the system is constant
no effect on the first law
flat line on P-V graph
defn + first law of thermodynamics: isovolumetric/isochoric processes
how does this appear on a P-V graph?
no change in volume
first law: delta U = Q (the change in internal energy is equal to the heat added to the system)
vertical line on a P-V graph
why is there no work performed in an isochoric process?
what implication does this have on the P-V graph?
the gas neither expands nor compresses
the area under the curve is zero (which represents the work done by the gas)
defn: spontaneous process
one that can occur by itself without having to be driven by energy from an outside source
how do we predict whether the process will be spontaneous or not?
by calculating the change in the Gibbs free energy (delta G) for a process
defn: coupling
a common method for supplying energy for nonspontaneous reactions by coupling nonspontaneous reactions and spontaneous ones
defn: state functions
certain macroscopic properties that describe the system in an equilibrium state
cannot describe the process, only useful for comparing equilibriums
defn: process functions
a way to quantitatively describe the pathway taken from one equilibrium state to another
what are the 2 most important process functions?
work (W) and heat (Q)
what are the 8 state functions + mnemonic for remembering them?
When I’m under PRESSURE and feeling DENSE, all I want to do is watch TV (temperature, volume) and get HUGS (enthalpy (H), internal energy (U), gibbs free energy, and entropy (S))
char (2): state functions
- when the state of a system changes from one equilibrium to another, one or more of these state functions will change
- they are independent of the path/process taken, but not necessarily independent of one another
defn: standard conditions
25 deg C (298 K), 1 atm pressure, and 1 M concentrations
defn: standard temperature and pressure
0 deg C (273 K) and 1 atm pressure
when are standard conditions used vs. STP used?
STANDARD conditions –> for kinetics, equilibrium, and thermodynamics
STP –> for ideal gas