Bellwork: What is the volume, in liters, of mol of oxygen gas at 20.0ºC and atm pressure? PV = nRT V = ? n = mol T = 20ºC = 293 K P = atm V= nRT P = mol (.0821 L·atm/mol·K) (293 K) atm = 6.17 L O 2
Ch Gases IV. Gas Stoichiometry
Gas Stoichiometry b Moles Liters of a Gas: STP - use 22.4 L/mol Non-STP - use ideal gas law b Non- STP Given liters of gas? start with ideal gas law Looking for liters of gas? start with stoichiometry conv.
1 mol CaCO g CaCO 3 Gas Stoichiometry Problem b What volume of CO 2 forms from 5.25 g of CaCO 3 at 103 kPa & 25ºC? 5.25 g CaCO 3 = mol CO 2 CaCO 3 CaO + CO 2 1 mol CO 2 1 mol CaCO g? L non-STP Looking for liters: Start with stoich and calculate moles of CO 2. Plug this into the Ideal Gas Law to find liters.
WORK: PV = nRTV = nRT/P V=(0.0525mol)(8.315L kPa/mol K)(298K) (103 kPa) V = 1.26 L CO 2 Gas Stoichiometry Problem b What volume of CO 2 forms from 5.25 g of CaCO 3 at 103 kPa & 25ºC? GIVEN: P = 103 kPa V = ? n = mol T = 25°C = 298 K R = L kPa/mol K
WORK: PV = nRT n = PV/RT n= (97.3 kPa) (15.0 L) (8.315L kPa/mol K) (294K) n = mol O 2 Gas Stoichiometry Problem b How many grams of Al 2 O 3 are formed from 15.0 L of O 2 at 97.3 kPa & 21°C? GIVEN: P = 97.3 kPa V = 15.0 L n = ? T = 21°C = 294 K R = L kPa/mol K 4 Al + 3 O 2 2 Al 2 O L non-STP ? g Given liters: Start with Ideal Gas Law and calculate moles of O 2. NEXT
2 mol Al 2 O 3 3 mol O 2 Gas Stoichiometry Problem b How many grams of Al 2 O 3 are formed from 15.0 L of O 2 at 97.3 kPa & 21°C? mol O 2 = 40.6 g Al 2 O 3 4 Al + 3 O 2 2 Al 2 O g Al 2 O 3 1 mol Al 2 O L non-STP ? g Use stoich to convert moles of O 2 to grams Al 2 O 3.