# Thermo, set 3

 .remove_background_ad { border: 1px solid #555555; padding: .75em; margin: .75em; background-color: #e7e7e7; } .rmbg_image { max-height: 80px; } enthalpy a convenient grouping of the internal energy, pressure, and volumeH = U + PV or h = u + pv [kJ/kg]Heat flow for process at constant pressureQ = change in enthalpy saturation pressure pressure at which the liquid and vapor phases are in equilibrium at given temp saturation temperature the temperature at which the liquid and vapor phases are in equilibrium at given pressure enthalpy of vaporization (latent heat of vaporization), h_fg - the amount of energy needed to vaporize a unit of mass of saturated liquid at a given temp /pressure moisture 1 - x, where x is quality x, or mg/mg+mf Lever Rule x = (y-yf)/yfgwhere y may be replaced with v, u, h, or s, and x is the mass of saturated vapor divided by total mass superheated given tempreature is greater than the saturation temp for given pressure compresed liquid when the pressure is greater than the saturation presure at a given temp How to choose the right table Compare the known state properties to the properties in the saturation region compressed liquid region v < vf saturation region vf < v < vg superheated region vg < v equations of state relationship between the state variables, temperature, pressure, and specific volume ideal gas law Pv = RTUsed when 1) pressure is small compared to critical pressure, 2) Temp is twice critical temp and pressure is less than 10 times critical pressure Gas constant R R = Ru/MRu is universal gas constant mass m = NM, the number of moles times the molar mass Combined gas law Ideal gas for a fixed mass - m1 = m2, or PV/RT (1) = PV/RT (2) 1st Law of Thermo Expression of the conservation of energy, energy can cross boundary of closed system as work or heat dU = d q - pdVIf energy transfer is due to temp. diff, it's heat, otherwise it's work. State function of energy - value depends on final and initial states, not on internal energy used Chemical potential proportionality constant m; change in internal energy is proportional to the number of particles dn added to the styem Combined 1st and 2nd laws dU = TdS – PdV + mdn Kelvin Statement It is not possible for the absorption of heat from a reservoir to complete convert to work Entropy measure of dispersal of energy (molecular disorder) Non-conserved property; as entropy increases, it increases entropy of universeIncreases as DOF increases Isentropic Entropy does not change (either by heat transfer or irreversibilities)Or, reversible adiabatic process Reversible Process ability to run a process back and forth infinitely without losses (i.e. perfect pendulum, mass on string, etc.) Irreversible Process i.e. dropping clay, hammering a nail, breaking glassSources; friction, pressure, voltage, temp, and concentration drops adiabatic no heat is gained or lost in a systemq=0 Engineering devices work best when isentropic and irreversibilities are eliminated Disorder naturally increases, and natural processor proceed spontaneously to order 2nd Law of Thermo entropy of isolated system, i.e universe, increases in any spontaneous changedeltaStot>0Entropy of universe continuously changingirreversible process of transferring heat from hot to cold body spontaneous process that occurs without ongoing outside interventioni.e. ice melting at room temperature, expansion of gas in space Molecular motion Translational - entire molecule moves Vibrational - within a molecule Rotational - 'spinning'motions 'shut down' as temp decreases -> reach perfect order Change in Standard Molar Entropy deltaSo =ΣnSo (products) -ΣmSo (reactants) 0th Law of Thermo Existence of equilibrium statesAll parts of closed equilibrium system are in a state of internal/heat equilibrium 3rd Law of Thermo Nernst-Plank heat theorem - entropy of system goes to zero if temp goes to zero .remove_background_ad { border: 1px solid #555555; padding: .75em; margin: .75em; background-color: #e7e7e7; } .rmbg_image { max-height: 80px; } AuthorKatieMac ID4943 Card SetThermo, set 3 DescriptionChemical Thermodynamics Updated2010-03-17T08:49:49Z Show Answers