Thermodynamics Flashcards
What is thermodynamic describe?
Processes that involve changes in temperature, transformation of energy, and the relationship between heat and work
What does the system boundary separate?
The system from the surroundings
What is the law of conservation of energy?
Energy can neither be created nor destroyed; it can only change form. The internal energy of the universe does not change. The energy lost by one must equal the energy gained by the other.
What is internal energy (U)?
Energies associated with the structure and motion of molecules within the system
What is internal energy as a state function?
(a state function) Change in internal energy depends only on the initial and final states and not on the path connecting these states. U system= U final-U inital
What can the internal energy of a closed system be changed by?
Transfer of work (w) and heat (q) between the system and its surrounding
What is the first law?
The change in internal energy of a closed system equals: U sys = q + w
What must happen when heat is lost by the system?
It must be complemented by an input of work to make up for the loss of heat (and conversely)
What is used to measure changes in energies at constant pressure?
The change in enthalpy
What does enthalpy as a state function mean?
Change in internal energy depends only on the initial and final states and not on the path connecting these states.
H system=. H final- H inital
What are the standard conditions for the standard enthalpy reactions?
289K
P= 1 bar
What is the standard enthalpy of formation?
Enthalpy associated with the formation of 1 mole of a substance from its element in their most stable form
What can the standard enthalpy of a reaction be determined from?
Standard enthalpy of formation
What does it mean if enthalpy change is less than 0 (
Reaction is exothermic
What does it mean if enthalpy change is more than 0 (>0)?
Reaction is endothermic
What happens if reaction losses heat?
Transfer of thermal energy from the system to the surroundings
What happens if the reaction gains heat?
Transfer of thermal energy from the surroundings to the system
What does the first law of thermodynamics not predict?
Which of several possible processes will occur (i.e. which one is natural or spontaneous)
What is the second law of thermodynamics state?
That the total entropy of a system and its surrounding always increases for a spontaneous process
What is entropy?
It is related to energy dispersal, measures the microscopic disorder of a system. Units J.K-1
What is the reaction if G
It is spontaneous
What is the reaction if G=0?
The reaction is at equilibrium
What is the reaction if G>0?
It is non spontaneous
What does it mean if the K»1?
Mixture will mainly consist of the products at equilibrium
