1. list 5 properties of gases 2. identify the various parts of the kinetic molecular theory 3....
TRANSCRIPT
Gas Laws: IntroductionAt the conclusion of our time together, you should be able to:
1. List 5 properties of gases2. Identify the various parts of the kinetic
molecular theory3. Define pressure4. Convert pressure into 3 different units5. Define temperature6. Convert a temperature to Kelvin
Importance of Gases
Airbags fill with N2 gas in an accident.
Gas is generated by the decomposition of sodium azide, NaN3.
2 NaN3 ---> 2 Na + 3
N2
General Properties of Gases
There is a lot of “free” space in a gas.
Gases can be expanded infinitely.
Gases fill containers uniformly and completely.
Gases diffuse and mix rapidly.
To Review
Gases expand to fill their containers
Gases are fluid – they flow Gases have low density
1/1000 the density of the equivalent liquid or solid
Gases are compressible Gases effuse and diffuse
Properties of Gases
Gas properties can be modeled using math. This model depends on —
V = volume of the gas (L) T = temperature (K)
› ALL temperatures in the entire unit MUST be in Kelvin!!! No Exceptions!
n = amount (moles) P = pressure
(atmospheres)
Ideal Gases
Ideal gases are imaginary gases that perfectly fit all of the assumptions of the kinetic molecular theory. Gases consist of tiny particles that
are far apart relative to their size. Collisions between gas particles and between particles and the walls of the container are elastic collisions
No kinetic energy is lost in elastic collisions
Ideal Gases (continued)
Gas particles are in constant, rapid motion. They therefore possess kinetic energy, the energy of motion
There are no forces of attraction between gas particles
The average kinetic energy of gas particles
depends on temperature, not on the identity of the particle.
Pressure
Is caused by the collisions of molecules with the walls of a container
Is equal to force/unit area SI units = Newton/meter2 = 1 Pascal (Pa) 1 atmosphere = 101,325 Pa 1 atmosphere = 1 atm = 760 mm Hg = 760
torr1 atm = 29.92 in Hg = 14.7 psi = 0.987 bar
= 10 m column of water.
Measuring Pressure
The first device for measuring atmospheric pressure was developed by Evangelista Torricelli during the 17th century.The device was called a “barometer”
Baro = weight Meter = measure
An Early Barometer
The normal pressure due to the atmosphere at sea level can support a column of mercury that is 760 mm high.
PressureColumn height measures
Pressure of atmosphere
1 standard atmosphere (atm) *
= 760 mm Hg (or torr) *= 29.92 inches Hg *= 14.7 pounds/in2 (psi)= 101.325 kPa
(SI unit is PASCAL)
= about 34 feet of water!
And now, we pause for this commercial message from STP
OK, so it’s really not THIS kind of STP…
STP in chemistry stands for Standard Temperature and Pressure
Standard Pressure = 1 atm (or an equivalent)
Standard Temperature = 0 deg C (273 K)
STP allows us to compare amounts of gases between
different pressures and temperatures
STP allows us to compare amounts of gases between
different pressures and temperatures
Let’s Review:Standard Temperature and
Pressure“STP”
P = 1 atmosphere, 760 torr T = 0°C, 273 Kelvins The molar volume of an ideal gas is 22.42 liters at STP
Pressure Conversions
A. What is 475 mm Hg expressed in atm?
B. The pressure of a tire is measured as 29.4 psi.
What is this pressure in mm Hg? = 1.52 x 103 mm Hg
= 0.625 atm475 mm Hg x
29.4 psi x
1 atm760 mm Hg
760 mm Hg 14.7 psi
101.325 kPa 14.7 psi
Pressure Conversions – Your Turn
A. What is 2.00 atm expressed in torr?
B. The pressure of a tire is measured as 32.0 psi.
What is this pressure in kPa?
= 1520 torr2.00 atm x 760 torr 1 atm
= 221 kPa32.0 psi x