1. Ch – Ideal Gases
-Avogadro’s Law (extension) -STP & molar volume of gas (review) -Ideal Gas Law (most important)

2. Avogadro’s Law
Equal volumes of gases contain equal numbers of molecules (moles)
at constant temp & pressure
true for any gas V n

3. 22.4 L Volume of Gas at STP At 1 atm and 273 K the volume of 1 mol
According to Avogadro’s law, 1 mole of any gas will occupy the same volume as one mole of any other gas at the same temperature and pressure
At 1 atm
and 273 K
the volume of 1 mol
of gas is
22.4 L

4. Volume of Gas at STP

5. PV=nRT P= pressure (atm) V=volume (L) n= number of moles
Ideal Gas Law
PV=nRT
P= pressure (atm)
V=volume (L)
n= number of moles
R=universal gas constant
T=temperature in Kelvins

6. PV = nRT (at STP and 1 mole)
How do we get R
PV = nRT (at STP and 1 mole)
(1.0 atm)(22.4L) = (1 mole)(R)(273K)
(1.0 atm)(22.4L) = R
(1 mole)(273K)

7. Universal Gas Constant R
R = Latm/molK or
R = J/molK

8. Ideal Gas Law Problems P = ? atm n = 0.412 mol T = 16°C = 289 K
Calculate the pressure in atmospheres of mol of He at 16°C & occupying L.
GIVEN:
P = ? atm
n = mol
T = 16°C = 289 K
V = 3.25 L
R = Latm/molK
WORK:
PV = nRT
P(3.25)=(0.412)(0.0821)(289)
L mol Latm/molK K
P = 3.01 atm

9. Cool Down
What pressure is exerted by mol of gas at 25 C if the gas is in a L container?
P = 16.9 atm