thermochemistry Flashcard

thermodynamics
study of energy transfer and energy transformation
energy absorbed/released
energy
ability to do work or to supply heat
work
when an object is moved by force over a distance
heat
difference in temperature when applied to energy
what are the two ways energy is transferred
heat and work
objects DON’T CONTAIN HEAT OR WORK!!
its internal energy that does
SI unit for energy
joules ??
kinetic energy
1/2 mv^2
kg, m/s
potential energy
everything needs to be stable so it goes to kinetic energy
chemical potential energy
interaction between particles in an atom
constant randomn motion so they have a kinetic energy>thermal energy
average KE is proportional to temp in gas
system in thermodynamcis
something is defined as system and everything else in surroundings
system is usually reactants and products
energy transferred between both
internal energy (U)
sum of potential and kinetic energy
change U= U final- U inital which is q+w
first law of thermodynamics>no energy lost
when heat or work goes into system
positive
when heat or work goes out of system
negative
in endothermic reactions
systems absorbs heat so it is positive; energy converted to chemical potential energy
in exothermic reactions
system releases heat so it is negative; energy converted to thermal
internal energy is what kind of system
state function; unique value once the conditions of system have been defined
geat and work are what kinds of system
no state functions bc they depend on the system
heat of reaction (q rxn)
heat transfer at constant temperature
heat reaction (q rxn) with constant volume
qv would just equal Q +W
no work is actually done so all energy is heat
heat reaction (q rxn) with constant pressure
Q= change U +pchange V
work equation
w= -p change V
enthaply (H)
U +PV; heat transfer at constant pressure
relationship with enthalpy and internal energy
changes in both equals each other
calorimeter definition
measurement of quantity of heat
heat capacity (C) and equation
heat required to change the temperature of a system by 1 degree c;
c=q/change in T
molar heat capacity
heat required to change the tempeature of system by 1 degree over 1 mole
specific heat capacity
heat capacity of 1 gram of sample
heat equation with specific heat
q= m (specific heat) (change in T)
MCAT
Coffee cup calorimeter
same as change H which is q+w; constant pressure
bomb calorimeter
constant volume; can be change in U + p change in V; but normally just

q+W

hess’s law
enthaply is state function so no matter the order or steps the energy with still be the same
standard condition
reference for thermo.
1 atm, 1 M, 25 degree C,
standard enthaply change
enthaply change when all reactants and products are in their standard states

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