Thermodynamics and Kinetics
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Define thermodynamics.
study of the flow of energy during chemical processes
Define open system.
exchanges matter and energy with its surroundings
Define closed system.
exchanges ENERGY but NOT MATTER with its surroundings
Define isolated system.
exchanges NEITHER MATTER NOR ENERGY with its surroundings
What is an extensive property? Provide examples.
an extensive property depends on the amount of matter present in the system e.g. mass, volume, internal energy, enthalpy, entropy, free energy, heat capacity
What is an intensive property? Provide some examples.
a property that does not depend on the amount of matter present in the system e.g. temperature, density. melting point
In thermodynamics, what is the difference between a process and a path?
process = net difference between final and initial states path = complete series of steps taken to get from the initial to the final state
What is the Zeroth Law?
if 2 systems are each in thermal equilibrium with a third system, they must all be in thermal equilibrium with each other i. e. all 3 systems would be at the same temperature e. g. if A and B are in equilibrium and B and C are in equilibrium, then A and C must also be in equilibrium
What is the difference between state function and path function?
state function = property that depends only on final and initial states (independent on path) path function = property that depends on the way in which the change is carried out (dependent on path)
List some state functions.
energy pressure temperature volume
List some path functions.
heat work distance frequency
What are 6 types of internal energy? Define them
electronic energy = attraction between electrons and their nucleus intermolecular potential energy = intermolecular forces rest mass energy = mass and energy are theoretically interchangeable(E= mc^2) vibrational energy = vibration of atoms around bonds rotational energy = rotation of molecule around its centre of mass translational energy =movement of the molecule
In the formula for pressure-volume work, what are the units of pressure? W = -PdeltaV
P= kPa
Define internal energy.
sum of all the kinetic and potential energy in a system
What is the formula used to find internal energy?
delta E = E final - E initial
There are only 2 ways to transfer internal energy. What are they?
heat or work
What is the First Law of Thermodynamics? What is the resulting formula?
total energy of the system and the surroundings is CONSTANT–> energy change in system must equal sum of the heat exchanged to/from the system and the work done on/by the system delta E = q+ W
What sign is given to endothermic processes? a) (+) b) (-)
a) (+)
What sign is given to exothermic processes? a) (+) b) (-)
b) (-)
Define enthalpy (H). What are the units? What is the formula?
total energy transferred during a chemical process, including the change in internal energy of the system (E) plus any energy (work) that is required to make room within the surroundings for the products of the rxn units: Joule delta H = delta E + W
Kinetic control leads to: a) the “easiest” product b) the most stable product
a) the “easiest” product
Thermodynamic control leads to: a) the “easiest” product b) the most stable product
b) the most stable product
What is Hess’ Law?
total enthalpy of an overall reaction is equal to the sum of the enthalpy changes for the individual steps delta H of reaction = sum of delta H
What is the standard enthalpy of formation (delta Hf) of a pure element in its standard state?
zero