Thermochemistry Flashcards
What does the first law state?
Energy can’t be created or destroyed
What is the equation of the internal energy of the system?
∆E = q+w
The work of a system =
-(P∆V), where P = pressure
What is ∆H?
Enthalpy
What is ∆H when Pressure is constant?
Gravity
What is it when a solid turns into a liquid?
Fusion / melting (+∆H)
What is it when liquid turns into a gas?
Vaporization / Boiling (+∆H)
What is it when a solid turns into a gas?
Sublimation (+∆H)
What is it when a gas turns into a liquid?
Condensation (-∆H)
What is it when a liquid turns into a solid?
Freezing (-∆H)
What is it when a gas turns into a solid?
Deposition (-∆H)
What are the types of systems found?
- Isolated
- Closed
- Open
What is an isolated system?
One which can’t exchange energy or matter with the surroundings
What is a closed system?
One that can exchange energy but not matter
What is an open system?
One that can exchange both matter and energy with the surroundings
∆H is
Enthalpy
∆S is
Entropy
∆G is
Standard Free Energy
Internal energy is the sum of
KE, PE, and chemical energies
Internal energy is
Constant
How do you measure change in enthalpy?
∆H prod - ∆H react
Isobaric processes are ones which occur at
Constant pressures
The heat given or absorbed within isobaric processes results in
Changes in enthalpy
Isochoric processes are ones which occur at
Constant volume
The heat given or absorbed within isochoric processes results in
Changes in internal energy
Isothermal processes are ones which occur at
Constant temperatures
Adiabatic processes are ones which occur when
No heat is exchanged between the systems and surroundings
In Adiabatic processes, the internal energy is equivalent to
Work
Hess’s Law states that
Enthalpies are additive
Entropy is the measure of
Disorder in a system
Which phase has the most disorder?
Gas
Which phase has the least disorder?
Solid
Maximum entropy is accomplished at
Equilibrium
∆Suniverse equals to
∆S system + ∆S surroundings, equalling to 0
Entropy is a
State function
What are the three laws of Thermodynamics?
- Conservation of Energy
- All spontaneous processes are ∆S system + ∆S surroundings > 0
- Entropy of perfectly crystalline substance at 0K is 0
Gibbs Free Energy communicates how
Changes in enthalpy and entropy affect reactions
What is the equation for Gibbs Free Energy?
∆G = ∆H - T∆S
What happens if ∆G is negative?
Reaction is spontaneous and moves forward
What happens if ∆G is positive?
Reaction is not spontaneous and moves in reverse
What happens if ∆G is 0?
System is in equilibrium
What does spontaneity indicate?
It reaction will occur
What happens when -∆H and -∆S?
Spontaneous at low temperatures
What happens when -∆H and +∆S?
Spontaneous at all temperatures
What happens when +∆H and +∆S?
Spontaneous at high temperatures
What happens when +∆H and -∆S?
Nonspontaneous at all temperatures
What is a process in which no heat is exchanged?
Isothermal
