All About Gases
The van der Waals equation uses the constants an and b to modify the ideal gas equation and better model the properties of real gases . What property of real gases does each constant account for?
a= attractive forces
b= repulsive forces
Diathermic vs. Adiabatic
diathermic: when two bodies are brought into contact with each other and the transfer of energy through heat is allowed
adiabatic: no energy flow is is possible between the two objects in contact even if the two objects have different temperatures
What is the value of delta H knot of an element in its standard state?
zero!
what is a thermodynamically spontaneous process?
a process that occurs without the surroundings having to do work on the system.
what dependence does an integrated rate law show?
it shows how concentrations vary with time.
Explain the combined gas law.
The combined gas law is an equation that combines all other gas laws. P1V1/T1=P2V2/T2.
Open- matter + energy can be transferred
Closed- only energy is transfeerred out
Isothermal- neither matter or energy is transferred
explain endothermic vs exothermic. Include terms regarding Delta H and products vs. reactants.
exothermic: releases heat. Delta H < 0. products have less energy than reactants.
endothermic: takes in heat. Delta H > 0. products have more energy than reactants.
under what conditions does the change in Gibbs energy for a process predict the spontaneity of the process?
Constant temperature and pressure
Delta G < 0 its spontaneous
Delta G = 0 its at equilibrium
Delta G > 0 its not spontaneous
what is the differential rate law
rate= k[A]m[B]n
explain when attractive forces are dominant and when repulsive forces are dominant.
Z > 1 repulsive forces dominate
Z = 1 ideal gas
Z < 1 attractive forces dominate
what are the properties of a system?
1. Pressure
2. Temperature
3. Amount in moles
4. Volume
what is entropy?
its a measure of disorder. Delta S
under what conditions does the change in Helmholtz energy for a process predict the spontaneity of the process?
Constant temp and volume
is activation energy always positive or negative?
Activation energy is always positive so the slope will always be negative.
how do you find DeltaU?
Delta U = 0 if there is no temp change
of Delta U=qv
which type of expansion yields the max amount of work?
reversible expansion
if a process is spontaneous what do we know about Delta S universe, surroundings, and system
Delta S system > -Delta S surroundings.
Delta S universe > DeltaS system + DeltaS surroundings
what is the equation for Delta S system?
Delta S system= nRln(vf/vi)
How do you find Ea, A, and the Arrhenius Plot?
The Arrhenius plot is found by plotting the ln(k) vs (1/T). The Ea is found by plugging the slope in as Y and using the equation slope=-Ea/R. A is found by using the Y-intercept=Ae(-Ea/RT)
How do you find q and w?
using the equation q=-w
therefore they are the same number just one is negative
compare and contrast temperature and heat.
heat is a form of energy
temperature is the measure of how concentrated the energy is
explain the process to find the standard enthalpy of formation.
1. write the balanced formula
2. line all the equations up on top of each other and cross out like terms (do not forget to switch around problems and switch the signs of the delta rH)
4. add all the standard enthalpies together (answer in kJ)
explain a phase diagram
first line is the solid line. First point is the triple point. Line going straight up is the liquid line. Line curving up is the vapor line. super critical fluid exists above the gas line. VP curve is the whole line. degrees of freedom find using F=C-P+2
explain how to find K.
ln[A]/[A]0=-kt