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Level 77

Ideal Gases


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ideal gas
a gas in which the particles undergo elastic collisions (when particles collide, there is no loss in the speed of the particles)
real gas
a gas that does not behave completely according to the assumptions of the kinetic-molecular theory
kinetic molecular theory
a theory based on the idea that particles of matter are always in motion
ideal gas law
law that states the math relationship of pressure (P), volume (V), temperature (T), the gas constant (R=0.0821), and the number of moles of a gas (n); PV=nRT.
Gay Lussac's Law
A gas has a pressure of 0.12 atm at 21.0° C. What is the pressure at 0.0°C ?
kmt
Tiny and far apart
Boyle's Law
A container holds 500. mL of CO₂ at 742 torr. What will be the volume of the CO₂ if the pressure is increased to 795 torr?
Charle's Law
As Volume increases temperature increases as long as pressure is held constant. V1/T1=V2/T2
Combined gas law
A combination of Boyle's Law, Charles' Law, and Lussac's Law. V1P1/T1=V2P2/T2 (people vomit over toilets)
Gas
Solid, liquid, or gas? The particles are moving fast enough to break any attraction between them.
Pressure
force per unit area
Temperature
? T :: ? collisions :: ? rate of reaction
Volume
A measure of space (lwh)
Diffusion
Ability of gases to mix
effusion
A process by which gas particles pass through a tiny opening
Expansion
Takes the whole volume of the container that holds them
compression
The part of a longitudinal wave where the particles of the medium are close together.
high kinetic energy
able to move fastly
760mmHg
1 atm
Dalton's Law
Law of Partial pressures
Pressure Tempreture Volume Mass
4 properties of a gas
pressure=
force/area
What causes pressure?
collisions occur on container walls and exert a force as they change in momentum.
n
amount of gas in moles
Na
Avogadro's constant = 6.02x10^23 particles per mol
1 mole
the amount of substance that has the same number of particles as there are atoms in 12g of carbon 12
Charles Law
A law stating the ratio between the volume and temperature of a gas is constant. This means that the greater the temperature, the greater the volume and vice versa.
Conditions for ideal gases
the pressure is not too large and the temperature is much higher than the boiling point
collisions are not perfectly elastic
Why some KE is lost in real gases
At -273 C
at absolute zero where pressure and volume become zero
Why kelvin scale is useful
its not pressure dependant and has a triple point where ice water and steam can coexist
Boltzman's constant k
1.38 x 10^-23
Boltzmans constant units
Joules per Kilogram
RAVED
Ideal gas assumptions(acronym)
Temperature of gas in kelvin
Mean Transitional Kinetic Energy is directly proportional to
the energy a molecule has
what the transitional kinetic energy is
ways to find the average
add up all kinetic energies
Monatomic Molecules have
Have only transitional kinetic energy
Diatomic Molecules have
both transitional and rotational kinetic energy
3/2 k is directly proportional to
Mean Kenetic energy of the atom
share Kenetic energies
air of mixed gases
Mass(M)
how to work out n
few molecules have high/low speeds
observations from a SPEED OF GAS MOLECULES graph
the average value
MEAN SPEED ( c )
pV = ¹/з Nmc²
alternate equation for kenetic theory
R and units
Molar gas constant
pressure (P)
the force acting on a unit of area of a surface; caused by collision of molecules
Barometer
a device that measures atmospheric pressure
Manometer
a device that measures the pressure in a container
pascal (Pa)
the SI unit of pressure; 1 Pa = 1 N/m^2
standard atmosphere (atm)
the average atmospheric pressure measured at sea level and 0C, defined as 1.01325 x 10^5 Pa.
millimeter of mercery (mmHg)
a unit of pressure based on the difference in the heights of mercury in a barometer or manometer.
torr
760
Charles's Law
A sample of oxygen occupies a volume of 160 mL at 91°C . What will be the volume of oxygen when the temperature drops to 0.00°C ?
Avogadro's law
the law that states that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules
standard temperature and pressure (STP)
0ºC/ 237 K- Temperature and 100kPa -Pressure
Standard molar volume
22.4 liters
universal gas constant (R)
a proportionality constant that relates the energy, amount of substance, and temperature of a system.
system
the identified object or collection of objects that will interact. The thing upon which forces acts. Synonymous with object
surroundings
all parts of the universe other than the system being considered.
Internal Energy
The sum of the kinetic energies and potential energies of all the atoms and molecules in a substance.
heat (q)
energy that transfers from one object to another because of a temperature difference between the objects
work (w)
the energy transferred when an object is moved by a force.
law of conservation of energy (first law of thermodynamics)
a basic observation that the total energy of the universe is constant.
joule (J)
The unit used to measure energy.
calorie (cal)
a unit of energy defined as exactly 4.184 joules; originally defined as the heat need to raise the temperature of 1g of water 1C.
state function
a property of the system determined by its current state, regardless of how it arrived at that state.
pressure-volume work (PV work)
a type of work in which a volume change occurs against an external pressure.
enthalpy (H)
a thermodynamic quantity that is the sum of the internal energy plus the product of the pressure and volume.
change in enthalpy (delta H)
the change in internal energy plus the product of the constant pressure and the change in volume; the heat lost or gained at constant pressure.
exothermic process
a process that occurs with a release of heat to the surroundings and therefore a decrease in the enthalpy of the system (delta h < 0).
enthalpy diagram
a graphic depiction of the enthalpy change of a system.
endothermic process
a process that absorbs heat from the surroundings
7.2k
What is the temperature of 0.80 mol of a gas stored in a 275 mL cylinder at 175 kPa?
V ∝ n
Which proportionality applies to Avogadro's law?
the temperature of the gas
Average kinetic energy of gas particles depends on
11.9 L
A balloon contains 0.350 mol of Ar at 5.00°C and 68.0 kPa pressure. What is the volume of the gas?
35.4 kPa
A sample of 4.75 mc024-1.jpg 10-3 mol of gas has a volume of 600 mL at 265°C. What is the pressure of the gas in kPa?
It has increased slightly.
A gas has experienced a small increase in volume but has maintained the same pressure and number of moles. According to the ideal gas law, how has the temperature of the gas changed?
V=bT
Charles's Law
V=an
Avogadros's Law
Universal gas constant
This is equal to 8.314 Joules per mole Kelvin, symbol R
0.57 mol
A sample of hydrogen gas, H2, has a volume of 8.56 L at a temperature of 0 degrees Celcius and a pressure of 1.5 atm. Calculate the number of moles of H2 present in this gas sample.
299 degrees K; 299-273=26 degrees celcius
A weather balloon contails 1.10 x 10^5 mol He and has a volume of 2.70 x 10^6 L at 1.00 atm pressure. Calculate the temperature of the helium in the balloon in kelvins and in Celsius degrees.
Ideal Gas Law Calculations Involving Conversion of Units
What volume is occupied by 0.250 mol carbon dioxide gas at 25 degree celcius and 371 torr?
Using the Ideal Gas Law Under Changing Conditions
Suppose we have a 0.240-mol sample of ammonia gas at 25 degree celcius with a volume of 3.5 L at a pressure of 1.68 atm. The gas is compressed to a volume of 1.…
Calculating Volume Changes Using the Ideal Gas Law
A sample of diborane gas, B2H6, a substance that bursts into flames when exposed to air, has a pressure of 0.454 atm at a temperature of -15 degrees celcius and a volume of 3.4…
partial pressure
pressure that the gas would exert if it were along in the container
Dalton's Law of Partial Pressures
indicates that pressure depends on the total number of gas particles.
Using Dalton's Law of Partial Pressures, I
Mixtures of helium and oxygen are used in the "air" tanks of underwater divers for deep dives. For a particular dive, 12 L of O2 at 25 degrees celcius and 1.0 atm and …
Using Dalton's Law of Partial Pressures, II
A sample of solid potassium chlorate, KClO3, was heated in a test tube and decomposed according to the reaction: 2KClO3 (s) -> 2KCl (s) + 3O2 (g)
0
…late the partial pressure of O2 in the gas collected and the number of moles of O2 present. The vapor pressure of water at 22 degree celcius is 21 torr.
meaning of temperature
measure of motion of gas particles
kelvin temperature of gas
directly proportional to average kinetic energy of the gas particles
relationship b/n pressure and temperature
if pressure is due to collision with walls, gas pressure should increase as temperature is increased
relationship between volume and temperature
volume of gas will increase as we raise its temperature at a constant pressure
Using Kinetic Molecular Theory to Explain gas Law Observations
Use the KM theory to predict what will happen to the pressure of a gas when its volume is decreased (n and T constant). Does this prediction agree with the experimental observations?
Gas Stoichiometry: Calculating Volume
Calculate the volume of oxygen gas produced at 1.00 atm and 25 degrees celcius by the complete decomposition of 10.5 g of potassium chlorate. The balanced equation for the reaction is: 2KClO3 (s) + 2KCl (s) + 3O2 (g)
Molar volume
At 273°K one mole of a gas occupies 22.4 dm3
stand temperature & pressure
0 degree celcius and 1 atm
Gas Stoichiometry: Calculations Involving Gases at STP
A sample of nitrogen gas has a volume of 1.75 L at STP. How many moles of N2 are present?
Gas Stoichiometry: Reactions Involving Gases at STP
Quicklime, CaO is produced by heating calcium carbonate, CaCO3. Calculate the volume of CO2 produced at STP from the decomposition of 152 g of CaCO3 according to the reaction:
Random walk
Aimless path molecules take
Kelvin
the most commonly used temperature scale in science, defined such that absolute zero is 0K and water freezes at 273.15K
Two kinds of gas pressures
Vapor Pressure & Atmospheric Pressure
Rebound
Gas particles move in a straight line until they collide with other particles and _______ in a different direction
Four variables that can be measured/changed
Temperature, # of moles, volume, pressure
Liters
Volume units
Atm
What is the largest unit of pressure that we have learned?
vaporization
change from a liquid to a gas
Vapor pressure
Force exerted by vapor particles directly above a liquid
greatest
Only particles with the _______ amount of KE will evaporate.
increases
leaving group ability _______ across a row and down a column
Gravity
is a force that attracts all objects toward each other
Air pressure
Collisions of particles around earth
altitude
Air pressure is affected by...
14.7 pounds per square inch
How much force does air exert on 1 square inch at sea level?
re-establish equilibrium in pressure
Why do ears pop when on an airplane?
Eustachian tubes
Connect inner ear to throat
Sinuses
Areas where gas molecules can collect and collide
Vacuum
Empty space where there are no gas molecules to collide with anything
How do suction cups work?
They create small vacuums because they force air out and then the air pressure and collisions outside of the vacuum keep it like that.
Explain the soda can implosion.
Heat evaporates liquid, created gas particles and collisions, then gas particles condensed when placed in cold water and the can imploded
PV = nRT
Equation for gas law
22.4 liters
volume of 1 mole of gas at STP
14.7
_______ pounds per square inch
101.3
_______ kilopascals per 1 atm
760
_______ mmHg per 1 atm
Down - fewer particles pushing down
The column of Hg would go (up/down) if placed on a mountain
Explain how a mercury barometer works.
atmosphere pushes down on Hg in bowl which then moves up to low pressure in the tube -- Mercury rises to 760 mmHg at sea level
The balloon would expand because the pressure outside the balloon is less when the gas particles are removed.
Describe what would happen to a balloon that is placed under a bell jar that is connected to a vacuum pump.
Describe what would happen to your ear if you were higher than sea level.
More particles are inside your ear than in the atmosphere so they pop to regain equilibrium
Aneroid barometer
Amount of collisions due to air pressure is detected by a sensitive metal diaphragm which controls a pointer on a scale
Kelvin from Celsius
C + 273
p
momentum
T
t or f
R
clockwise
Plane elevation goes up, pressure drops
Explain why planes must be pressurized when they fly higher.