Unit 8 Stoichiometry and gas laws
Name:
Period:
Remember that at STP gas is 22.4 L = 1 mol :
Worksheet: Molar Volume/Molar Mass #1
1. How many moles are contained in 78.4 L of Neon at STP?
L
2. What is the volume(L) of 0.8 moles of Chlorine gas at STP?
22.4
mol
g
3. How many particles are contained in 16.8 L of Xe at STP?
From PT
Molar mass
mol
4. How many grams are contained in 39 L of F2 gas at STP?
Molecules, ions
particles
5. What is the volume of 192 g of O2 at STP?
6.02 x 1023
6. How many molecules are contained in 168 L of CO2 at STP?
7. What is the mass of 40.34 x 1023 H2 molecules at STP?
8. How many molecules are contained in 5.6 L of H2 at STP?
Density of a gas calculations: Density of a gas = molar mass(g/mol) / ( 22.4 L/mol)
1) What is the density of a gas with a molar mass of 17 g/mol at STP?
2) What is the density of a gas with a molar mass of 23 g/mol at STP?
mol
Unit 8 Stoichiometry and gas laws
Solutions for when gases are not at STP
3) What is the volume of a gas that has a density of 1.96 g/L and a molar mass of 29 g/mol?
4) What is the volume of a gas that has a density of 0.96 g/L and a molar mass of 35 g/mol?
5) What is the molar mass of a gas with a density of 2.9 g/Land a molar volume of 44.8 L/mol?
6) What is the molar mass of a gas with a density of 0.5 g/L and a molar volume of 11.2 L/mol?
Gas Stoichiometry and use of Ideal gas law to solve problems(solve for n(moles) using n= PV/RT first)
1. Calculate how many grams of methane (CH4) are in a sealed 800. mL flask at room temperature (22 °C)
and 780. mmHg of pressure. R = 62.4 L*mmHg/mol*K
2. Dry ice is carbon dioxide in the solid state. 1.28 grams of dry ice (CO2 ) are placed into a 5.00 L
evacuated chamber that is maintained at 35.1°C. What is the pressure in the chamber in atm after all the
dry ice has sublimed into CO2 gas? R= 0.0821 L*atm/mol*K
3. A student conducts the following reaction in the lab at STP:
2SO2(g) + O2(g)  2 SO3(g)
She reacts 5.0 L of sulfur dioxide (SO2) with excess oxygen at constant temperature and pressure. How
many liters of sulfur trioxide (SO3) will she produce? (Use mole ratio step)
4. A student conducts an experiment by collecting NO2 gas at STP and uses excess oxygen:
N2 + 2 O2  2NO2
How many liters of NO2 gas is produced from 3.4 L of N2
Unit 8 Stoichiometry and gas laws
IB Supplemental:
Gas law and stoichiometry problems
5. A student collected a sample of NO2 gas at 1.05 atm and 299 K making 45 L of NO2. How many
grams of N2 were used assuming O2 was in excess? R= 0.0821 L-*atm/mol*K
N2 + 2 O2  2NO2
a) Solve for moles of NO2 first using PV=nRT
b) Then use stoichiometry to solve for moles of N2 used and then convert to grams using molar mass of N2
6. A student collected a sample of P2O5 gas at 0.91 atm and 287 K making 1.7 L of P2O5. How many
grams of O2 was needed assuming phosphorus was in excess R= 0.0821 L-*atm/mol*K
P4 + 5O2  2P2O5
c) Solve for moles of P2O5 first using PV=nRT
d) Then use stoichiometry to solve for moles of O2 and convert to grams using molar mass of O2
7. A student collected a sample of NH3 gas at 303.7 kPa and 235 K making 8.7 L of NH3. How many
grams of H2 were needed assuming nitrogen was in excess? R= 8.31 L-*kPa/mol*K
N2 + 3H2  2NH3