Gases Flashcards
Kinetic molecular theory
- collection of particles are in constant motion
- no attraction or repulsions between molecules; they collide like billiard balls
- large amount of space between particles relative to the size of the particles themselves
- Particles move with increased speed when temp. is increased.
Gas molecules are in ____________.
constant motion
What happens when gas molecules move and strike a surface?
they push or exert force on a surface.
Define pressure
the total amt. of force exerted by gas molecules hitting the entire surface at any one instant
How is pressure found?
P=F/A
P= pressure
F= force
A= area
How is pressure created with a gas?
it is the result of the constant movement of gas molecules and collisions with the surfaces around them.
What are the factors that the pressure of a gas depends on?
1) the number of gas particles in a given volume
2) volume of the container
3) average speed of the gas particles
How is air pressure measured?
with a barometer
How does a barometer work?
A column of mercury is supported by air pressure. The force of the air on the surface of the mercury balanced by the pull of gravity on the column of mercury.
An increase in particle in a volume of space will increase what?
pressure
atm
atmosphere
1 atm (exactly) = 760 (exactly) mmHG = 760 torr (exactly) = 14.7 psi, lbs/in squared
What are the common units of pressure?
Pascals (Pa) Kilopascals (kPa) Atmosphere (atm) Millimeters of mercury (mmHg) Inches of Mercury (inHg) Torr (torr) Pounds per square inch (psi, lbs./in squared)
mmHg
Millimeters of mercury
1 atm (exactly) = 760 (exactly) mmHG = 760 torr (exactly) = 14.7 psi, lbs/in squared
torr
Torr (unit of pressure)
1 atm (exactly) = 760 (exactly) mmHG = 760 torr (exactly) = 14.7 psi, lbs/in squared
psi
Pounds per square inch
1 atm (exactly) = 760 (exactly) mmHG = 760 torr (exactly) = 14.7 psi, lbs/in squared
Boyle’s Law
- Pressure of a gas is inversely proportional to its volume.
- temp is constant
- amt. of gas is constant
- as P increases V decreases by same factor
- PxV= constant
What is the formula for Boyle’s law?
P1xV1=P2xV2
According to Boyle’s law what happens when the volume a gas occupies is cut in half?
the pressure of the gas is doubled (as long a temperature and amt. of gas stays the same.)
Charles’ law
- Volume is directly proportional to temperature
- Pressure is constant
- amt. of gas is constant
- as T increases, V increases
- V= constant x T
- TEMP IS ALWAYS MESURED IN KELVINS
According to Charles’ law what happens to a gas when it is heated, when it is chilled?
When heated the gas expands and density decreases, when chilled the gas condenses and density increases.
What is the Formula for Charles’ law?
V1/T1 = V2/T2
According to Charles’ law density decreases when a gas is heated, why?
because the molecules have a higher kinetic energy and they have more energy to push out.
What is the combined gas law?
Boyle’s law and Charles’ law put together; this law predicts what will happen to the volume of a gas when temp. and pressure changes.
What is the formula for the combined gas law?
(P1)(V1)/(T1) = (P2)(V2)/(T2)
All gas laws are only valid with __________.
Kelvins
Avogadro’s law
Volume is directly proportional to the number of gas molecules.
- V= constant x n
- P and T are constant
- more gas molecules larger volume
- number of gas molecules is counted in moles.
What is the formula for Avogadro’s law?
V1/n1 = V2/n2
Ideal Gas law
- all the gas laws combined
- R is gas constant
- R depends on P and V but 0.0821 atmxL/molxK will be used
- because of this P needs to be in atm and V needs to be in liters
When is the ideal gas law used and when is the combined gas law used?
the ideal gas law is used when a gas is at one condition, the combined gas law is used when a gases’ condition is changing.
What is the formula for the Ideal gas law?
PV = nRT
What are ideal gas conditions?
- high temperature
- low pressure
- particle size is small compared to space between particles
- interactions between particles are insignificant
What are Real (non-ideal) gas conditions?
- low temp
- high pressure
- particle size is signif. compared to space btwn. particles
- interactions btwn. particles are signif.
What is partial pressure?
Each gas in a mixture exerts a pressure independent of the other gases in a mixture. The pressure of a component gas in a mixture is called a partial pressure. The sum of all the partial pressures is equal to the total pressure.
Dalton’s Law of partial pressure
P total = P gas A + P gas B + P gas C + ….
How do you find a partial pressure?
multiply the total pressure of a gas mixture by the percent turned into a decimal of the fractional component of the mixture.
P He = (0.800)(1.0 atm) = 0.80 atm
(The component gas = percent divided by 100) to get decimal
What partial pressure of O2 are our bodies adapted to breath?
0.21 atm
hypoxia
low oxygen levels in blood; partial pressures of O2 less than 0.1 will lead to hypoxia, unconsciousness or death
When climbers are climbing mt. Everest they need O2 cylinders to prevent what?
hypoxia
When you feel the pressure of air what is felt?
one pressure; not individual pressures
The higher the percentage of a gas in a mixture the more it ______ to total pressure of the mixture.
contributes
Standard conditions
- keeping conditions the same
- STP
STP
Standard temp. and pressure.
-standard pressure 1.00 atm
-standard temp. 273 K
0 degrees C
How much volume will one mole of any gas at STP occupy?
22.4 L (THIS IS CALLED MOLAR VOLUME) and can be used as a conversion factor. As long as work is done at STP
1 mol = 22.4 L
Molar volume
There is so much room between molecules in the gaseous state that volume is not effected by the size of molecules (under ideal conditions).
