gas stoichiometry
DESCRIPTION
Gas Stoichiometry. Molar Volume of Gases. The volume occupied by one mole of a gas at STP (standard temperature and pressure) Equal to 22.4 L / mol Can be used as a conversion factor OR. Sample Problem 1. - PowerPoint PPT PresentationTRANSCRIPT
Molar Volume of Gases
• The volume occupied by one mole of a gas at STP (standard temperature and pressure)
– Equal to 22.4 L / mol
– Can be used as a conversion factor
– ORgas 1mol
L 22.4
L 22.4
gas mol 1
Sample Problem 1
• A chemical reaction produces 0.0680 mol of oxygen gas. What volume in liters is occupied by this gas sample at STP?
x = 1.52 L O2
Sample Problem 2
• A chemical reaction produced 98.0 mL of sulfur dioxide gas, SO2, at STP. What was the mass of the gas produced?
• Thought process: mL L mol g
98.0 mL = 0.098 L
x x = 0.280 g SO2
PRACTICE: You Try It!
1. What is the volume of 77.0 g nitrogen dioxide gas at STP? 37.5 L NO2
2. At STP, 3 L of chlorine is produced during a chemical reaction. What is the mass of this gas? 9 g Cl2
Gas StoichiometryMoles Liters of a Gas:
– STP Conditions• use 22.4 L/mol and stoichiometry
– Non-STP Conditions• use ideal gas law and stoichiometry
General rule: FIND MOLES FIRST!– If given volume of gas – Non-STP
1. Use ideal gas law to find moles 2. Use stoichiometry to convert moles to final answer
– If given volume of gas – STP 1. Use molar volume (22.4 L/mol) to find moles2. Use stoichiometry to convert moles to final answer
Gas Stoichiometry– If you need the volume of gas – Non-STP
1. Use stoichiometry to convert to moles of needed gas2. Use the ideal gas law to find volume
– If you need the volume of gas – STP
1. Use stoichiometry to convert to moles of needed gas2. Use the molar volume (22.4L/mol) to find volume
1 mol C2H6
30.08 g C2H6
Gas Stoichiometry ProblemHow many liters of CO2 form when 15.25 g of
C2H6 combusts at STP?
15.25 g C2H6
1
= 1.014 mol CO2
2C2H6 + 7O2 6H2O + 4CO2
4 mol CO2
2 mol C2H6
Need: liters 1. Use stoich to calculate moles of CO2
2. Use the molar volume to find liters
Use the molar volume to find liters.
22.4 L CO2
1 mol CO2
Gas Stoichiometry ProblemHow many liters of CO2 form when 15.25 g of
C2H6 combusts at STP?
1.014 mol CO2
1
= 22.71 L CO2
2C2H6 + 7O2 6H2O + 4CO2
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
1 mol CaCO3
100.09 g CaCO3
Gas Stoichiometry ProblemWhat volume of CO2 forms from 5.25 g of CaCO3 decomposing at 103 kPa & 25ºC?
5.25 g CaCO3
1
= 0.0525 mol CO2
CaCO3 CaO + CO2
1 mol CO2
1 mol CaCO3
Need: liters 1. Use stoich and calculate moles of CO2., 2. Use the ideal gas law.
Plug this into the Ideal Gas Law to find liters.
WORK:
Convert units first!
Then apply PV = nRT
Ans: 1.26 L CO2
Gas Stoichiometry Problem• What volume of CO2 forms from 5.25 g of
CaCO3 at 103 kPa & 25ºC?
GIVEN: P = 103 kPa V = ? n = 1.26 mol T = 25°C R = 0.0821 Latm/molK
WORK:
Convert units first!
Then apply PV = nRT
Gas Stoichiometry ProblemHow many grams of Al2O3 are synthesized from 15.0 L of O2
at 97.3 kPa & 21°C?
GIVEN:P = 97.3 kPaV = 15.0 Ln = ?T = 21°C R = 0.0821 Latm/molK
Al + O2 Al2O3 Given: liters
1. Use Ideal Gas Law and calculate moles of O2.,
2. Use stoich to find grams of Al2O3
NEXT use stoich to find grams
2 mol Al2O3
3 mol O2
Gas Stoichiometry Problem How many grams of Al2O3 are formed
from 15.0 L of O2 at 97.3 kPa & 21°C?
0.597 mol O2
1
= 40.6 g Al2O3
4 Al + 3 O2 2 Al2O3
101.96 g Al2O3
1 mol Al2O3
Use stoich to convert moles of O2 to grams Al2O3.
You Try It!!
• Find the volume of hydrogen gas made when 38.2 g zinc reacts with hydrochloric acid at a pressure of 107.3 kPa and a temperature of 88oC.
• HINT: – Use stoich to find moles of H2 first, then use the
ideal gas law.
Zn (s) + 2 HCl (aq) ZnCl2(aq) + H2(g)
ANSWER: 16.3 L H2