Atom – smallest piece of an element
Molecule – smallest piece of a compound – two or more atoms chemically bonded
Mole – counting number equal to 6.022 x 10 23
Molar Mass – number of grams of a substance per mole – equal to the atomic mass on the periodic table
How many moles in 5.5g of hydrogen gas?
How many molecules in 2.5 moles of oxygen?
What is the mass of one molecule of helium gas?
Matter is made of particles in continuous motion
Particles move in random directions at a variety of speeds
Particles of gases are on average very far apart from one another
Molecules of gases interact only when they collide
Collisions are perfectly elastic (no loss of kinetic energy)
1atm = 760mmHg = 760torr = 101kPa
STP – standard temp and pressure (0 ° C and 1 atm)
Volume is proportional to the temperature –
Charles Law ( V
1
/T
1
= V
2
/T
2
)
Volume is inversely prop to temp – Boyles Law
( P
1
V
1
= P
2
V
2
)
Pressure is prop to temp – Gay-Lussac’s Law
( P
1
/T
1
= P
2
/T
2
)
Combined Gas Law puts them together
( P
1
V
1
/T
1
= P
2
V
2
/T
2
)
One that follows all kinetic theory
Volume of a gas also depends on the number of moles
Ideal Gas Law
PV = nRT R = .0821 L •atm/ mol•K
Determine the volume of 1.00 mole of a gas at
STP.
A container of oxygen at STP has a volume of
10.0 L. What is the mass of the gas?
A helium party balloon has a radius of 18.0cm at 20 ° C and 1.05 atm. How many moles of He are in the balloon and what is the mass of the gas in the balloon?
An auto tire is filled to a pressure of 200kPa at
10 ° C. After driving 100km, the temp rises to
40 ° C. What is the pressure now?
The average KE of molecules is directly proportional to the temp
KE = ½ mv 2 = 3/2 kT k – Boltzman’s Constant = 1.38x10
-23 J/K
What is the average KE of gas molecules at
37 ° C?
Also called root mean square velocity
v rms
= 3 kT
M m – mass (in kg) of one molecule of the gas
What is the rms speed of an oxygen molecule at 20 ° C?