Gas Stoichiometry
Ideal Gas Law
Gas Stoichiometry

The Ideal Gas Law
• Putting It All Together
•PV = nRT n = moles P = pressure
Temp = must be in Kelvin
Volume = must be in Liters
Should be able to solve for any R but you won’t have to

• Use STP
Solving for R values

PV = nRT
1) Straight Ideal Gas law problem:
Sprinkled all over the AP => another way to get moles.
2) Problem: Got moles, Do stoich!

Sample Problem 1
• For an ideal gas, calculate the pressure of the gas if 0.215 moles occupies 338 mL at
32 ° C.

Sample Problem 2
• Acetic acid reacts with solid sodium carbonate.
• 5.00 grams of sodium carbonate is added to 20.0 mL of
1.50 M acetic acid. What volume of CO
0.878 atm and 23 ° C?
2 is produced at

Sample Problem 3
• Sodium metal is added to water.
• If 43.2 mL of hydrogen gas are produced at 767 torr and 59 ° C in excess water, how many grams of sodium were reacted?

Finding the Molar Mass of a
Gas
• Should be provided grams of the gas
• Use PV = nRT to find the moles
• MM = grams moles

Manipulation of the Ideal Gas Law
#1
PV = nRT n= mass mole mass so…….
PV = mass RT mole mass

Manipulation of the Ideal Gas Law
#2
PV = nRT n= mass mole mass
P = (mass R T)
(volume x mole mass) or
P = (density R T) mole mass
MM = DRT
P

Manipulation of Ideal Gas Law
• The density of a gas was measured at 1.50 atm and 27 ° C and found to be 1.95 g/L.
Calculate the molar mass of this gas.

Dalton Law of Partial Pressures
Key: P total
= P
1
+ P
2
+ P
3
+….
The total pressure = the sum of all the partial pressures

Dalton Law of Partial Pressures
Manipulation
P total
= P
1
+ P
2
+ P
3
+….
P total
= n
1
RT + n
2
RT + n
3
RT +…..
V V V
Sum of the moles of gases; who cares what they are

Application of Dalton’s Law of
Partial Pressures
HUGE!
Collecting pressure over water
P gas
P air
P water

Collecting pressure over water
P air
= P gas
P air
P gas
+ P water
P water
P water is dependent on temperature