Gases Flashcards
two factors that determine the state of a substance
- the forces holding the particles tother
- the kinetic energy of the particles
ionic forces
- intramolecuclar
- usually solid state
- NaCl
Polar (dipole-dipole) forces
- intermolecular
- can be anything, usually liquid or gas
- HCL (g)
Dispersion force
- intermolecular
- liquid or gas
- CO2 (g)
What is the kinetic molecular theory?
all substances contain entities that are in constant motion
3 types of entity motion
- vibrational
- rotational
- translational
what particles have a vibration motion?
all particles
what particles have a rotational motion?
- liquids
- solids
- some solids
what particles have a translational motion?
- only in liquids and gases
temperature definition
a measure of the average kinetic energy of the entities of a substance
What is the kinetic molecular theory?
- the volume of an individual gas moecule is negligible
- there are no attractive nor repulsive forces between gas molecules
- gas molecules move randomly in all directions, in straight lines
- when gas molecules collide, they don’t loose kinetic energy
- ideal gases, do not condense into liquids when cooled
- the average kinetic energy of a gas molecule is directly related to the temperature. The greater the temperature, the greater the average motion of the molecules and the greater their kinetic energy
KMT describes a hypothetical gas called an ideal gas
i deal particles take up hardly any space
Who came up with kinetic molecular theory?
Robet Brown
pressure definition
the force exerted on an object per unit of surface area (P = F/A)
common SI unit of measurement of pressure
the pascal Pa = 1N/m^2
how is the pressure of a gas determined
by the kinetic moition
what device is used to measure pressure
a barometer
Describe the mercury barometer
- a closed tube is filled with mercury, then inverted into a pan
- gravity pulls the mercury downwards, but pressure pushes on the mercury in the pan, keeping it inside the tube
- the result is that we can measure the height of the Hg( mm) in the tube as a measure of pressure
mass of atmosphere
5.1 * 10^18 kg
= 1000 kg over an area of 1 m^2
Why is there lower pressure the higher up in the atmosphere you are?
there is lass atmosphere above, less atmosphere pushing down
what is atmospheric pressure
the force exerted on Earth’s surface by a column of air over a given area (101 325 N/m^2). Pressure is exerted equally in all directions
standard pressure and pressure at sea level
101.325 kPa
One atmosphere = ________kPa
101.325
STP
Standard Temperature and Pressure
at 0 degrees celsius and 101.325 kPa
SATP
standard ambient temperature and pressure
at 25 degrees celsius and 100.00 kPa
Why is SATP better than STP?
SATP more conveniently resembles lab conditions
1 atm to ________ mmHg
650 mm Hg
1 Torr = ________ mmHg
1
psi = ________ Pa
6895
Boyle’s Law
As pressure on a gas increases, the volume fo the gas decreases proportionally, if temperature and amount of gas (moles) remain constant.
Boyle’s law equation
P1V1=P2V2
Describe flying and pressure and ascending
as atmospheric pressure, decreases, the relative pressure inside the ear becomes hgiher and pushes out the eardrum
Describe flying and pressure and descending
as atmospheric pressure increases, the relative pressure inside the ear decreases.
Large pressure differentials cuases pain and even a rupture of the eardrum
Describe the creation of the celsius scale
- Anders Celsius created the scale by taking a thin glass tube filled with mercury and recording the height of the liquid in ice cold water, repeated in boiling water
divided distace between 2 heights in 100 divisions = 1 degree
Charles’ Law
As the temperature of a gas increases, the volume increases proportionally when pressure and mount of gas remains constant
V1/T1 = V2/T2
Gay-Lussac’s Law
the pressure of a fixed amount of gas, at a constant volume is directly proportional to its kelvin temperature
P1/T1 = P2/T2
combined gas law
the product of the pressure and volume of gas divided by its absolute temperature is a constant as long as the amount of gas is kept constant
P1V1/T1 = P2V2/T2
volume ratio
when measured at the same temperature and pressure, volumes of gaseous reactants and products of chemical reactions are always in simple ratios of whole numbers
who came up with law of combining volumes
Joseph Gay-Lussac and Amedeo Avogadro
Avogadro’s Law
the volume of a gas is directly proportional to the amount of gas, when temperature and pressure remain constat.
V1/n1 = V2//n2
molar volume
the space that is occupied by one mole of gas
same for all gases
measured in L/mol
what is molar volume of an ideal gas at STP?
22.4 L
what is molar volume of an ideal gas at SATP?
24.8 L
problems with real gas behaviours at high pressures and low temperature
- in very smalll volumes there will be many more interactions and collisions
- the volumes of the gas molecules is now a significant fraction of the container
R
the universal gas constant
8.214 kPa *L/mol *K
the ideal gas law
PV = nRT
what is pressure caused by?
collisions with the walls of the container
Dalton’s law of partial pressures
the total pressure of a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases
atmospheric pressure
N2 = 78.08%
Ar = 0.93%
O2 = 20.95%
CO2 = 0.03%
= 101.3 kPa
