CHEM 301 UNIT 1
Molecular weight
"MWT" "mm" =(m/n)
Metacognition
"Thinking about thinking" or the ability to evaluate a cognitive task to determine how best to accomplish it, and then to monitor and adjust one's performance on that task
STANDARD PRESSURE
1 atm = 760mmHg = 760torr Pressure= Force/ Area 1STP= 101,325
IDEAL GAS LAW
PV=nRT WHERE R = 0.08206 atm L Ideal Gas is amazing - empirically derived and also theoretically derived.
Apply the ideas of kinetic molecular theory to a variety of gas phenomena.
particles are moving at distribution of velocities •The particles are so small compared with the distance between them that the volume of the individual particles can be assumed to be negligible (zero) •The particles are in constant motion. The collisions of the particles with the walls of the container are the cause of the pressure exerted by the gas. •The particles are assumed to exert no forces on each other; they are assumed to neither attract nor repel each other. •The average kinetic energy of a collection of gas particles is assumed to be directly proportional to the Kelvin temperature of the gas.
The average kinetic energy of the gas particles depends only on the _________ of the system.
temperature
COMBINED GAS LAW
(CHARLES + BOYLE'S LAW) P1V1/T1- P2V2/T2
VAN DER WAALS
(P+an^2/v^2)(V-nb)=nRT a= polarity, attraction b= size
number density vs. mass density
- Number density: # of moles(fixed # of particles)/particles within a given volume. d: n/v=P/RT Same p and t (ideally)= same # density (# of particles) -Mass density is d=m/v. Same t and p (ideally) = same # density but different mass density because different gases have different masses per particles. density: g/v=mmP/RT Use density to determine molecular weight (m/n)
The basic postulates of kinetic molecular theory can be given as follows:
-A pure gas consists of a large number of identical particles (molecules), separated by distances that are large compared with their size. -The molecules of a gas are constantly moving in random directions with a distribution of speeds. -The molecules of a gas exert no forces on one another except during collisions, so that between collisions they move in straight lines with constant velocities. -The collisions of the molecules with each other and with the walls of the container are elastic; no energy is lost during a collision.
STP and SATP
-standard temperature and pressure (273.15K and 1 bar) [.986atm and 0˚C] -standard ambient temperature and pressure (298.15K (25˚C)) and (1 bar)
KINETIC MOLECULAR THEORY
1) GASES ARE SMALL AND SPACED FAR APART (2) COLLISIONS ARE PERFECTLY ELASTIC- NO ENERGY IS LOST OR GAINED (1/2)M1V^2= (1/2)M2V^2
Apply the concept of a scientific model to explain data not previously studied in class.
Description of nature that can describe a lot of different situations.
NON IDEAL GASES
HIGH PRESSURE LOW VOLUME LOW TEMPERATURE
EFFUSION
IS THE ESCAPE OF GASES THROUGH TINY HOLES
DIFFUSION
IS THE MIXING OF GASES
Partial pressure vs. total pressure
In Dalton's law Pi=(Xi)(P total) The total pressure of a mixture of gas is the sum of the partial pressure of its components.
Avogadro's law
States that the volume of gas at constant temperature and pressure is proportional to the number of moles (n) of the gas, that is, V = k(constant)n. V=k(n) n1/V1=n2/V2, 1 mol = 22.4 L (STP) 6.02 * 10^23 (used for atoms)
DALTON'S LAW OF PARTIAL PRESSURE
TOTAL PRESSURE IS THE SUM OF THE PRESSURES THAT EACH GAS WOULD EXERT IF IT WERE ALONE Ptotal= P1+P2+P3 P1=NRT/V n=PV/RT
Temperature and velocity of a gas
The higher the temperature, the faster the velocity because it causes the particles to move faster. ??
Mole fraction
Xi=ni/ntotal (n is percentage per mole?) The mole fraction takes a fraction of the amount of total pressure and calculates the partial pressure. Xi cannot be > 1.
Based on the Kinetic Molecular Theory of gases decreasing the volume of a gas at constant temperature will lead to a higher pressure because
The reduced volume will lead to more collisions of the gas particles with the walls of the container resulting in a higher pressure
Student centered learning
the students and their needs are the focus and the teacher becomes the facilitator among them; the students are active participants in the learning process
Kinetic Molecular Theory
A theory that explains that the behavior of physical systems depends on the combined actions of the molecules constituting the system. 1. All gas particles are in constant, random motion 2. No loss of energy when particle collisions occur 3. The volume of the gas molecules in a gas is negligible; only take into account space between 4. Gases have no intermolecular attractive or repulsive forces, As heat is increased, molecules move faster and farther apart. Temperature increases, volume increases, but density decreases As heat is decreased, molecules move slower and closer together. Temperature decreases, volume decreases, but density increases.
Explain when and why the ideal gas model fails to predict the behavior of gases observed in nature and in the laboratory.
At high pressure because: The particles are assumed to exert no forces on each other; they are assumed to neither attract nor repel each other.
Explain the VanderWaal's Equation and relate it to the Hard Sphere Model.Daadgaetheathat
Attractive forces have effect on behavior- high pressure, low temperature. ( P + (a(n^2))/(v^2))(v-nb)=nRT a- experimentally derived constant Relates to HSM- can no longer ignore the volume that gas particles take up when computing volume. This formula includes the constant b to correct for the PAR between gas particles????
Kinetic energy can be passed from one object to another. Collisions are:
Effectively elastic collisions(an encounter between two bodies in which the total kinetic energy of the two bodies after the encounter is equal to their total kinetic energy before the encounter), in which kinetic energy is preserved. In inelastic collisions, kinetic energy is dissipated in various forms of energy, such as heat, sound, binding energy (breaking bound structures).
Hybrid learning
Instructional format that combines elements of face-to-face teaching and learning with elements of distance education. Also known as blended learning.
Flipped classroom
Inverting traditional teaching methods (such as lectures), delivering instruction online outside of class and moving "homework" into the classroom
KINETIC ENERGY
KE= 1/2MV^2 KEavg= 3/2 RT Vrms=SQROOT (3RT/MW) R=8.314
Explain how T, V, and n affect the pressure as described by kinetic molecular theory.
Kinetic theory explains macroscopic properties of gases, such as pressure, temperature, or volume, by considering their molecular composition and motion. Essentially, the theory posits that pressure is due not to static repulsion between molecules, as was Isaac Newton's conjecture, but due to collisions between molecules moving at different velocities through Brownian motion.
Under what condition does the Ideal Gas Equation of State, best model the real gas behavior?
Low pressure P increases - V decreases V = constant/P As P gets very large, V goes to zero! The available volume is the volume of the container minus the volume of the particles low Pressure = Large Volume "volume" of particles doesn't matter
Molar Mass vs. Velocity
Pressure is proportional precisely to the number of collisions times the impact of collisions. So: more massive particles= fewer collisions. # of collisions scales inversely with velocity.
GAS LAWs QUANTIFY:
THE RELATIONSHIP OF THE PROPERTIES. EQUATION FORM OF LAWs GIVE ABILITY TO PREDICT CONDITIONS AT NEW STATE.
Explain the general principles of the hard sphere model of a gas.
The Hard Sphere model corrects for the fact that the space that the molecules occupy matters, and thus the measured volume is no longer the volume that is available to the gas particles in a particular sample. P(V-nb) = nRT or V = Vig(intended amount) + n(moles)b(constant)
Kinetic Energy vs. Temperature of Gas
The higher the temperature, the higher the kinetic energy KE=3/2RT because the faster the velocity and kinetic energy is related to mass and velocity KE=1/2mv^2 Temperature is directly proportional to KE and change's its average KE.
Describe the distribution of velocities for the particles in a gas sample and what factors affect this distribution.
The molecules are moving at a distribution of speeds in random directions. Gases consist of large numbers of molecules (or atoms, in the case of the noble gases) that are in continuous, random motion. Usually there is a great distance between each other, so the molecules travel in straight lines between abrupt collisions at the walls and between each other. These collisions randomize the motion/speed of the molecules.
Explain what the breakdown of the ideal gas law tells us about the assumptions of kinetic molecular theory.
The pressure of a gas results from collisions between the gas particles and the walls of the container. Each time a gas particle hits the wall, it exerts a force on the wall. An increase in the number of gas particles in the container increases the frequency of collisions with the walls and therefore the pressure of the gas. Amontons' Law (P & T) average kinetic energy of a gas particle depends only on the temperature of the gas. Thus, the average kinetic energy of the gas particles increases as the gas becomes warmer. Because the mass of these particles is constant, their kinetic energy can only increase if the average velocity of the particles increases. The faster these particles are moving when they hit the wall, the greater the force they exert on the wall. Since the force per collision becomes larger as the temperature increases, the pressure of the gas must increase as well. Boyle's Law (P = 1/v) Gases can be compressed because most of the volume of a gas is empty space. If we compress a gas without changing its temperature, the average kinetic energy of the gas particles stays the same. There is no change in the speed with which the particles move, but the container is smaller. Thus, the particles travel from one end of the container to the other in a shorter period of time. This means that they hit the walls more often. Any increase in the frequency of collisions with the walls must lead to an increase in the pressure of the gas. Thus, the pressure of a gas becomes larger as the volume of the gas becomes smaller. Charles' Law (V T) The average kinetic energy of the particles in a gas is proportional to the temperature of the gas. Because the mass of these particles is constant, the particles must move faster as the gas becomes warmer. If they move faster, the particles will exert a greater force on the container each time they hit the walls, which leads to an increase in the pressure of the gas. If the walls of the container are flexible, it will expand until the pressure of the gas once more balances the pressure of the atmosphere. The volume of the gas therefore becomes larger as the temperature of the gas increases. Avogadro's Hypothesis (V N) As the number of gas particles increases, the frequency of collisions with the walls of the container must increase. This, in turn, leads to an increase in the pressure of the gas. Flexible containers, such as a balloon, will expand until the pressure of the gas inside the balloon once again balances the pressure of the gas outside. Thus, the volume of the gas is proportional to the number of gas particles. Dalton's Law of Partial Pressures (Pt = P1 + P2 + P3 + ...) But the pressure due to the collisions between the original ball bearings and the walls of the container would remain the same. There is so much empty space in the container that each type of ball bearing hits the walls of the container as often in the mixture as it did when there was only one kind of ball bearing on the glass plate. The total number of collisions with the wall in this mixture is therefore equal to the sum of the collisions that would occur when each size of ball bearing is present by itself. In other words, the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual gases.
Pressure from macro and micro view
macro: P=F/A By moving rapidly in all directions, the atoms of gas are able to fill any container in which they are placed. When the atoms hit a wall of the container, they bounce off, colliding elastically-microscopic level accounts for the pressure exerted by the gas on the macroscopic level. The micro is average pressure exerted by the molecules as they collide elastically with the walls of their container. From this the macro view of pressure is simply that the total pressure is equivalent to P=F/A. The gas can be easily compressed because there is plenty of open space between the atoms. Reducing the volume merely reduces that empty space. The liquid and the solid are not nearly so easy to compress because there is little or no empty space between the atoms. You may have noticed that although our sub-microscopic model can explain many of the properties of solid, liquid, and gaseous mercury, it cannot explain all of them.
mindset
the cognitive view individuals develop for themselves that either is fixed or involves growth, & a habitual or characteristic mental attitude that determines how you will interpret and respond to situations
Charles law
the law that states that for a fixed amount of gas at a constant pressure, the volume of the gas increases as the temperature of the gas increases and the volume of the gas decreases as the temperature of the gas decreases, V₁/T₁=V₂/T₂ FOUND THAT THE VOLUME OF A GAS INCREASES LINEARLY WITH TEMPERATURE. (V=bT) - After plotting this relationship for many gases, it was noticed that each volume extrapolated to zero at the same temperature, -273.15)
Boyle's law
the law that states that for a fixed amount of gas at a constant temperature, the volume of the gas increases as the pressure of the gas decreases and the volume of the gas decreases as the pressure of the gas increases, P₁V₁=P₂V₂
Kinetic Molecular Theory
•The particles are so small compared with the distance between them that the volume of the individual particles can be assumed to be negligible (zero) •The particles are in constant motion. The collisions of the particles with the walls of the container are the cause of the pressure exerted by the gas. •The particles are assumed to exert no forces on each other; they are assumed to neither attract nor repel each other. •The average kinetic energy of a collection of gas particles is assumed to be directly proportional to the Kelvin temperature of the gas.
