Studied by 14 people
thermodynamics
the study of heat and its transformations
thermochemistry
changes in heat that take place during chemical process
kinetic energy
the energy of motion
potential energy
stored energy
system
part of the universe we are studying
surroundings
the rest of the universe
1 joule (J) =
1 kg m^2/s^2
calorie
the amount of energy needed to raise the temperature of 1 g of water 1 degree C
1 calorie (cal) =
4.184 J
1 nutritional Calorie (Cal) =
1000 cal
S°
standard entropy
G°
standard Gibbs free energy
c
specific heat capacity
H°
standard enthalpy
q
heat
Gas constant R (in terms of J per mol K)
8.314 J mol^-1 K^-1
KE
kinetic energy
T
temperature
n
moles
m
mass
delta G° =
delta H° - T delta S°
calorimetry
laboratory technique used to measure the heat released or absorbed during a chemical or physical change
heat capacity
the quantity of heat needed to change the temperature 1 K
heat capacity =
q/delta T
heat capacity units
J/K
specific heat capacity (c)
quantity of heat needed to raise the temperature of 1 g of a substance 1 K
equation for specific heat
q=cm delta T
specific heat capacity units
J/g · K
molar heat capacity (C)
amount of heat needed to change the temperature of 1 mol of a substance by 1 K
what are two types of calorimeters
coffee-cup calorimeter and a bomb calorimeter
coffee-cup calorimeters have constant
pressure
bomb calorimeters have constant
volume
coffee-cup calorimeters are used to measure
changes in reactions that are open to the atmostphere and the specific heats of solids
describe the basic functioning of a coffee calorimeter
a known mass of a solid is heated to a certain temperature than added to a known mass of water at a known temperature in the calorimeter. the final temperature is recorded
bomb calorimeters are used to measure
energy changes in combustion reactions
describe the basic functioning of a bomb calorimeter
compressed oxygen is added to a weighed sample, which is ignited by hot wire. the temperature change of the calorimeter and a known mass of water is measured
First Law of Thermodynamics
the total energy of the universe is constant
Entropy (S)
the disorder of a system
Second Law of Thermodynamics
all processes that occur spontaneously move in the direction of an increase in entropy of the universe
what is the entropy of the universe for a reversible process
0
what is the entropy of the universe for a spontaneous process
greater than 0
what are 4 rules that can be used to determine the change in entropy
entropy increases with an increse in molecules, temperature, when gas is formed from a liquid or solid, and when liquid is formed from a solid
enthalpy change (delta H)
the heat gained or lost by a system under constant-pressure conditions
when delta H is greater than 0 the reaction is
endothermic
when delta H is less than 0 the reaction is
exothermic
thermochemical equations are restricted to
moles
negative delta H values are usually associated with
spontaneous reactions
enthalpy change is dependent on the state of
matter
Hess’s law
if a reaction occurs in a series of steps, then the enthalpy change for the overall reaction is the sum of the enthalpy changes of the individual steps
state function
a function that only depends on the initial and final states and not the pathway
enthalpy change is a
state function
standard enthalpy of formation
change in enthalpy when 1 mol of the substance if formed from its elements when all substances are in their standard states
standard state of a gas
1 atm
stadard state of an aqueous solution
1 M
standard state of a pure substance
1 atm and 25 degrees C
standard molar entropies (S°)
entropies associated with 1 mol of a substance in its standard states
the standard enthalpy of formation of an element in its standard state is
0
Gibbs free energy (G)
thermodynamic function that combines enthalpy, entropy, and temperature
if delta G is greater than 0,
the reaction is not spontaneous
if delta G is less than 0,
the reaction is spontaneous
if delta G is equal to 0,
the reaction is at equilibrium
equation for delta G under nonstandard conditions
delta G° + 2.303 RT log Q
measurements needed in a thermodynamics experiment
mass, possible volume, initial and final temperature
energy
the capacity to do work or to produce heat
work
force acting over a distance
work equation
W=-P change in V
potential energy
due to position or composition (stored energy)
kinetic energy
energy due to motion of the object
state function
value that depends on the state of the substance, not how that state was reached
heat and temperature exchanges accompany which four processes?
heating and cooling a substance, phase change, dissolving solutes, chemical reactions
describe solute and solvent interactions in exothermic reactions
solute and solvent particles are more strongly attracted to each other than they are to themselves
are bonds or attractive forces being formed or broken in exothermic reactions
formed
how does the temperature of the surrroundings change in exothermic reactions
increase
how does the temperature of the surrroundings change in endothermic reactions
decrease
are bonds or attractive forces being formed or broken in endothermic reactions
broken
describe solute and solvent interactions in endothermic reactions
solute and solvent particles are more strongly attracted to themselves than they are to each other
are decomposition reactions usually endo or exothermic?
endothermic
are synthesis reactions usually endo or exothermic?
endothermic
how can dissolving an ionic compound be both a physical and chemical change?
evaporation is a physical process, but bonds are boken which is a chemical process
intensive properties
properties independent of the amount of the substance
are specific and molar heat capacity intensive or extensive properties?
intensive
write an equation relating heat loss to heat gain
heat lost = -heat gained
how does the value of the heat of fusion for melting versus freezing?
heat of fusion is postive when melting and negative when freezing
describe the mathematical process when calculating the energy required to melt a substance
slope: q=mc delta T
straight line: q=(moles)(heat of fusion)
add up the values
equation for enthalpy
H=E+PV
bond enthalpy
energy stored in a chemical bond
standard heats of formation
the amount of heat needed to form 1 mole of a compound from its elements in their standard states
Hess’s law
if you add chemical equations to get an overall equation, then you can also add the heat changes to get the overall heat change
Internal Energy (E)
Internal Energy (E)
Note 
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