1. 7-4 Avogadro’s Principle (Section 13.4 )
And you!

2. Avogadro’s Principle states that for a gas at constant temperature and pressure, the volume is directly proportional to the number of moles of gas. In equation form:
Volume = constant x moles
or V = constant x n

3. Rearranging gives us:
V1 = constant = V2 or V1 = V2
n n n1 n2
Another way to interpret this principle is:
equal volumes of different gases (at constant T and P) have the same number of molecules.

4. 7-5 The Ideal Gas Law (Section 13.5)
It’s possible to combine all the gas laws we’ve learned into one expression called the Ideal Gas Law:
PV = nRT
P = pressure V = volume (in L) (= STP)
n = number of mole T = temperature (in K)
R = the Universal Gas Constant =
L•atm = L•kPa = L•mmHg
mol•K mol•K mol•K
All the gas laws can be derived from the Ideal Gas Law; for example, by holding V and n constant.

5. The Ideal Gas Law can be used to calculate additional quantities other than P, V, and T:
Using the idea that the molar mass (formula weight) = grams/mole or MM = grams/n
Therefore: n = g/mm
Sub in for n gives: PV = g •RT MM
so MM = gRT/PV !!!!!
Used to identify the type of gas you have based on the calculated MM and the periodic table values!!!!

6. Rearrange for Density:
d = g/ml so d = g/V
MM = g RT so g/V = mm/ (RT/P)
V P
Density of gas = (g/V) = P(MM) / RT

7. Last section of notes 7-5 At STP T = 273K and P = 1 atm
PV = nRT so V = nRT/P
If n = 1 mole: V = 1(.0821)(273)/1 = L
So 36 g H2O (1 mol/18.02g) = 2 moles H2O
V = 2 (.0821)(273) / 1 = 44.8 L