# Molar Mass from Periodic Table

```CHAPTER 11 – IDEAL GAS LAW
AND GAS STOICHIOMETRY
11.1- Mass and Volume of Gases
Avogadro’s Principle = Equal volume of gases at
same T and P have same numbers of molecules
H2
He
O2
N2
All of these balloons are the same size (same volume)
All of these balloons are at the same Temperature and Pressure inside
All of these balloons would have the same number of MOLECULES
BUT…These balloons would have DIFFERENT masses!
11.1- Mass and Volume of Gases
1 mol of anything = 6.02 x 1023 particles
1 mol of any gas = same number particles = 6.02 x 1023 particles
= same volume
= different mass
Molar Volume = Volume of 1 mole of any gas at STP
22.4 L = 1 mole of gas at STP
1 m ole
2 2 .4 L
22.4 L
1 m o le
11.1- Mass and Volume of Gases
Examples:
11.1- Mass and Volume of Gases
Gas Density
-Depends on T and P
-We will start by looking at density at STP
dSTP = Molar Mass
Molar Volume
Examples:
11.1- Mass and Volume of Gases

Examples: dSTP
11.1- Mass and Volume of Gases
Molar Mass
MM = dSTP * Molar Volume
(will be given)
11.2 - Ideal Gas Law
Used on ONE gas at ONE set of conditions
PV = nRT
Pressure
Volume
R = 0.08206 L atm /mol K
= 62.4 L mmHg / mol K
= 8.314 L KPa / mol K
Temperature
moles
Ideal Gas Constant
11.2 - Ideal Gas Law
How do you know which R to pick???
R = 0.08206 L atm /mol K
= 62.4 L mmHg / mol K
= 8.314 L KPa / mol K
By the
PRESSURE UNIT!!
If Pressure is in mmHg…
Pick 62.4 L mmHg / mol K
If Pressure is in KPa…
Pick 8.314 L KPa / mol K
11.2 - Ideal Gas Law
Examples:
11.2 - Ideal Gas Law
Examples:
11.2 - Ideal Gas Law
Examples:
Non-STP Gas Density
d = MM * P
R*T
Examples:
(will be given)
Non-STP Molar Mass
MM = mass sample * R * T
P*V
Examples:
Will be given
11.3- Stoichiometry of Gases
-NEED BALANCED EQUATION!!
-Could include info from Chapter 3, 7,8,9, 10, or 11!!
11.3- Stoichiometry of Gases
Review:
Molar Mass from
Periodic Table
Grams
A
Moles
A
Ratio from
Balanced
Equation
Moles
B
Molar Mass from
Periodic Table
Grams
B
New Information:
With GASES…There are other options:
Moles to Volume using 22.4L/mole at STP or PV=nRT
Volume to Moles using 22.4L/mole at STP or PV=nRT
11.3- Stoichiometry of Gases
Molar Mass from
Periodic Table
Grams
A
Moles
A
Ratio from
Balanced
Equation
Moles
B
Molar Mass from
Periodic Table
22.4 L/mol IF at STP
22.4 L/mol IF at STP
OR
OR
PV=nRT if NOT STP
PV=nRT if NOT STP
Volume A
if a GAS
Volume B
if a GAS
Grams
B
11.3- Stoichiometry of Gases
Examples:
11.3- Stoichiometry of Gases
Examples:
11.3- Stoichiometry of Gases
Examples:
11.3- Stoichiometry of Gases
Examples:
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