Chapter 7: Thermochemistry Flashcards
What is the first law of thermodynamics?
∆U = Q - W
U = change in internal energy
Q = heat added
W = work done
____________ processes occur when the system’s temperature is constant.
isothermal
When U is constant, change in U is 0 and the first law simplifies to what?
Q = W
heat added equals work done by system
____________ processes occur when no heat is exchanged between the system and the environment. The thermal energy of the system is constant.
adiabatic
In adiabatic processes, Q = 0 and the first law simplifies to what?
∆U = -W
change in internal energy of system = work done on the system
____________ processes occur when the pressure of the system is constant. Does not alter first law.
isobaric
________________ processes experience no change in volume. No work is performed, so first law is:
isovolumetric; ∆U = Q
What is a common method for supplying energy for nonspontaneous reactions?
Coupling nonspontaneous reactions to spontaneous ones
What are the state functions?
When I’m under pressure and feeling dense, all I want to do is w
When I’m under pressure and feeling dense, all I want to do is watch TVand get HUGS
Pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, entropy
State functions describe what?
The system in equilibrium state
Standard conditions have been defined for measuring enthalpy, entropy, and Gibbs free energy. What are they?
25°C
1 atm pressure
1 M concentrations
used for kinetics, eq, and thermodynamics
Liquid to gase phase is known as ________________
evaporation, or vaporization
When liquid loses a high-energy particle, the temperature of the remaining liquid ____________.
decreases
Boiling can only occur ________ the boiling point of a liquid and involves vaporization through the entire volume of the liquid.
above
Gas back to liquid is ____________
condensation
The temperature at which the vapor pressure of the liquid equals the ambient pressure is called the ____________ point.
boiling
Transition from solid to liquid is ________
fusion, or melting
Liquid to slid is ____________
solidification, crystallization, or freezing
Solid to gas is ____________
sublimation
Gas to solid is ____________
deposition
The ____________ point is the temperature and pressure above which there is no distinction between the phases. This is where the phase boundary between gas and liquid terminate.
critical
Something above the critical point is called a ________________ fluid.
supercritical
Draw a phase diagram and label
The heat of vaporization at the critical point and for all temps and pressures above this point is ________.
zero
________________ is the average kinetic energy of particles in a substance.
temperature
____________ ____________ is the measure of the total kinetic energy of the particles in a substance
thermal energy
________________ measures the average kinetic energy of the particles in a substance
temperature
________ is the transfer of energy from one substance to another as a result of their differences in temperature.
Heat
The ________ law of thermodynamics implies that objects are in thermal equilibrium only when their temps are equal.
zeroth
The heat (q) absorbed or released in a given process is calcualted via what equation?
q = mc∆T
Specific heat is what?
The amount of energy required to raise the temperature of one gram of substance by one degree Celsius
What is H2O’s specific heat?
1 cal/g*K
While a glass of water and a pool have the same specific heat, they have different ________ ____________ - the produce mc (mass time specific heat)
heat capacities
How to solve for equilibrium temperature?
set q equal to each other
Phase change reactions do not undergo changes in temperature. You must use what equation?
q = mL = n∆H
m = mass in g, latent heat = enthalpy of an isothermal process
n= mol
When going from liquid to solid, change in enthalpy is ________ because heat is removed.
negative
When transitioning at the solid-liquid boundary, the enthalpy of ________ must be used to determine heat transferred during the phase change.
fusion
When transitioning at the liquid-gas boundary, the enthalpy of ________ must be used to determine heat transferred during the phase change.
vaporization
How do you find enthalpy change of a reaction?
∆Hrxn = Hproducts - Hreactants
What does a positive ∆Hrxn mean? Negative?
Positive = endothermic, negative = exothermic
Standard enthalpy of ____________ is the enthalpy required to produce one mole of a compound from its elements in their standard states.
formation; ∆H°f
The standard enthalpy of a ____________ is the enthalpy change accompanying a reaction being carried out under standard conditions.
reaction, ∆H°rxn
How standard enthalpy of a rxn calculated?
Difference between the sum of standard heats of formation for the products and sum of standard heats of formation of reactants
________ law states that enthalpy changes of reactions are additive.
Hess’s
Hess’s law applies to what?
enthalpy, entropy, and Gibbs free energy – any state function!
Hess’s law can also be expressed in terms of bond ____________, aka bond ________________ ____________. This is the average energy that is required to break a particular type of bond between atoms in the gas phase.
enthalpies, bond dissociation energy
The standard heat of ________________ is the enthalpy change associated with the combustion of a fuel.
combustion ; Typically occurs during oxygen
The ____________ law of thermodynamics states that energy spontaneously disperse from being localized to becoming spread out.
second
entropy
____________ is the measure of the spontanoeous dispersal of energy at a specific temperature: how much energy is spread out, or how widely spread out energy becomes, in a process.
Entropy
Gibbs free energy combines what 3 things?
temperature, enthalpy, and entropy
The free energy change of reactions can be measured under standard state conditions to yield the ____________ ________ ____________.
standard free energy, ∆G°rxn
