Flashcards in General Chemistry-Thermochemistry Deck (190)
What is the 1st law of thermodynamics?
Energy is never created nor destroyed but simply changed from one form to another
What is considered the system?
The matter that is being observed- the total amount of reactants and products in a chemical reaction.
Is the boundary between system and surrounding environment permanetly fixed?
No, it can be moved
What are the three characterizations of a thermodynamic system?
What is an isolated thermodynamic system? Example?
The system cannot exchange energy (heat and work) or matter with the surroundings; for example, an insulated bomb calorimeter.
What is a closed thermodynamic system? Example?
The system can exchange energy (heat and Work) but not matter with the surroundings, for example a steam radiator
What is an open thermodynamic system? Example?
The system can exchange both energy (heat and work) and matter with the surroundings, for example a pot of boiling water.
What is the definition of a process?
When a system experiences a change in one or more of its properties (such as concentrations of reactants or products, temperature, or pressure).
Association with a change of the state of a system
How are some processes unique?
Some processes are uniquely identified by some property that is constant throughout the process. Many of these processes create special conditions that allow the first law of thermodynamics to be simplified.
What is the simplified equation for the 1st law of thermodynamics?
/\U= Q - W
What do the letters represent in the simplified equation for the 1st law of thermodynamics?
/\U: The change in internal energy of the system
Q: is the heat added to the system
W: is the work done by the system
When do isothermal processes occur?
When the system's temperature is constant
What does constant temperature imply in a isothermal process?
The total internal energy of the system (U) is constant throughout the process
Why is the total internal energy of an isothermal system constant throughout the process?
Temperature and internal energy are directly proportional. When U is constant, /\U=0, and the first law simplifies to Q=W (the heat added the the system equals the work done by the system).
How does an isothermal process graph appear?
As a hyperbolic curve
What are the axes used to look at an isothermal process graph?
Pressure and volume (P-V Graph)
How is work represented on an isothermal process graph?
Work is the area under a curve
When does an adiabatic process occur?
When no heat is exchanged between the system and the environment; thus the thermal energy of the system is constant throughout the process.
When Q=0, how does the 1st law of thermodynamics simplify?
/\U = -W (the change in internal energy of the system is equal to the work done on the system [the opposite of work done by the system]).
How does adiabatic process appear on a P-V graph?
When do Isobaric process occur?
When the pressure of the system is constant
Which processes are common? Why
Isothermal and isobaric processes are common because it is usually easy to control temperature and pressure.
How do isobaric processes appear on a P-V graph?
Isobaric processes do not alter the 1st law of thermodynamics, but appear as a flat line.
What are isovolumetric processes?
Processes that experience no change in volume
What is another name for isovolumetric processes?
Why is no work performed in an isovolumetric process?
Because the gas neither expands nor compresses, no work is performed
How does the 1st law of thermodynamics simplify in an isovolumetric process?
/\U =Q (The change in Internal energy is equal to the heat added to the system.)
How does an isovoumetric process appear on a P-V graph?
Vertical Line. The area under the graph which represents work done is zero
How can processe by further classified?
Spontaneous or nonspontaneous