Physical Chemistry Unit 1 Exam

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Thermodynamics
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Study of the movement of energy; energy moves either through heat or work, or both
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Heat
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Movement of energy is chaotic, and is going all different directions
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Work
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Movement of energy that is direted motion; force; all the movement is going in one direction
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Classical Thermodynamics
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This is the study of thermodynamics that is only concerned with macrospoic properties, microscopic properties of materials (internal structure/atoms) don’t matter ( most of the time)
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System
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Part of the universe we are interested in; visualized as the front face of this particular cube Ex: Liquid in a beaker, gas in a piston
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Surroundings
Surroundings
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Rest of the universe apart from what we are interested in; outside of the cube completely
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Barrier
Barrier
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Associated with the system and surroundings; rests between them; represented visually by the side face of the cube (R)
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Open Barrier
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A barrier between the system and surroundings that allows for exchange of matter and energy Ex: Uncovered beaker
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Closed Barrier
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A barrier between the system and surroudnings that allows for exchange of energy but NOT matter, contains two subcategories
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Adiabatic Barrier
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A closed barrier that allows for energy to be exchanged btw the system and surroundings but ONLY through work Ex: Piston acting on gas in a container
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Diathermic Barrier
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A closed barrier that allows for energy to be exchanged btw the system and surroundings but ONLY through heat; Ex: test tube combustive reaction surrounded by a water bath at room temp
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Isolated Barrier
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A barrier that does NOT allow energy nor matter to pass; Ex: Thermos
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Dynamic Equilibrium (Equilibrium)
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Keeps the concentration of chemical molecules and the rates of movement equal; however, the molecules of the chemicals DO keep moving; constant diffusion
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State Variables
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Variables that depend on and describe the current state of the system; Ex: Volume, Pressure, Temperature
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State Equation
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An equation that consists ONLY of state variables and a constant Ex: Ideal Gas Law: PV=nRT
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Process (“Path”) Variables
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Variables that depend ONLY on the path taken by the system between equilibrium states; may (and often do) have different values at the same equilbrium state of a system; Ex: work, heat
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Example of Process (“Path”) Variables
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If the left corner is labeled point A, and an imaginary car drives around and stops at each vertex along the way, when the car returns to A the odometer will read 4 miles even though we are back in the initial position; whereas the GPS would read 0 miles away from home before you leave A and when you return to A
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Temperature
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Indicates the direction of heat flow
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Thermal Equilibrium
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Two objects temperatures do not change when they are brought into contact with each other
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Movement of Heat
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Heat will work on a gradient similar to that of a concentration and electrochemical gradient; heat will transfer from a hot object to a cold object until their temps are in equilibrium
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0th Law of Thermodynamics
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If A and B are in equilibrium, and B and C are in equilibrium, then A and C are also in equilibrium
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Applications of the 0th Law of Thermodynamics
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C allows for us to determine the temperature of A+B ; temperature exists and it can be measured
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Perfect Gases
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Described by the ideal gas law; gas mlcs are in constant and random motion (diminished or not present at all if attractive/repulsive forces are acting on the mlcs); mlcs act as point masses (take up no volume in space); collisions btw mlcs/wall are perfectly elastic (equal force and energy upon entrance and exit from collision)
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Real Gases
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Gases do not behave in an ideal manner due to attractive and repulsive forces; includes IMF (London dispersion forces, dipole-dipole, H-bonding)
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Real Gases and Forces
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*Attractive forces are much more significant and travel over longer distances, than the repulsive forces that affect the behavior fo the gasses*
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Repulsive Forces
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Volume that is taken up by the gas molecules itself; partial/full charges and their interactions
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Real Gas Deviation
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As real gasses approach higher and higher pressures, there is further deviation from the ideal gas laws
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Attractive Forces Consequence
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When these forces are acting on a gas, they promote compression of the gas
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Repulsive Forces Consequence
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When these forces are acting on a gas, they promote expansion of the gas
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Attractive and Repulsive Forces
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These forces both act over short distances within and btw the gas mlcs, but they can be ignored when the pressure is low
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Virial Eqn
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Modifies the ideal gas law by adding a power series incorporating experimentally derived constants; very accurate, but finding the appropriate coefficients at the specific temperature is difficult
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Van der Waals eqn
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Adds two coefficients to account for attractive and repulsive forces; more general and less precise than the Virial eqn; b represents repulsion, and a represents attraction; *CANNOT use extreme values for pressure, temperature, and volume*, a and b are indpendent from other variables
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Adiabatic Process
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Chemical process that occurs at constant heat
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Isothermal Process
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Chemical Process that occurs at constant temperature
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Isobaric Process
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Chemical process that occurs at constant pressure
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Isochoric Process
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Chemical process that occurs at constant volume
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Isenthalpic Process
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Chemical process that occurs at constant enthalpy (delta H)
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Isentropic Process
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Chemical process that occurs at constant entropy (delta S)
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Internal Energy
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Sum of all potential and kinetic energy internal to the system; state function; U=q+w
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First Law of Thermodynamics
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Internal energy of an isolated system is constant; can be thought of as a law of conservation of internal energy (Can’t add more energy to the system or take energy away from the system, the energy just changes while remaining in equilibrium)
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Expansion Work
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Work arising from a change in volume; dw=-pdV
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Reversible Processes
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We assume these processes behave as though they are in equilibrium; consider this is true at every point along the path of the process; Does the maximum work
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Constant Volume Heat Capacity
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Change in internal energy with respect to temperature at a constant volume
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Constant Pressure Heat Capacity
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Change in internal energy with respect to temperature at a constant pressure
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Enthalpy
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Energy supplied to a system as heat at constant pressure; state function: H=U+pV; can be measured using calorimetry (delta H=q (constant pressure))
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Standard Enthalpies
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Standard state of a substance is its pure form at the pressure of one bar and specified temperature (typically 298K)
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Enthalpy Changes
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Exist for chemical, state, and other types of change
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Hess’s Law
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Standard enthalpy of a rxn is the sum of standard enthalpies of the individual rxns into which a rxn may be divided

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