using The Ideal Gas Law Gas Stoichiometry
PV T VnVn PV nT Ideal Gas Law = k UNIVERSAL GAS CONSTANT R= L atm/mol K R=8.31 L kPa/mol K = R
Ideal Gas Law UNIVERSAL GAS CONSTANT R= L atm/mol K R=8.31 L kPa/mol K PV=nRT
GIVEN: P = ? atm n = mol T = 16°C = 289 K V = 3.25 L R = L atm/mol K WORK: PV = nRT P(3.25)=(0.412)(0.0821)(289) L mol L atm/mol K K P = 3.01 atm Ideal Gas Law b Calculate the pressure in atmospheres of mol of He at 16°C & occupying 3.25 L. IDEAL GAS LAW
GIVEN: V = ?V = ? n = 85 g T = 25°C = 298 K P = kPa R = 8.31 L kPa/mol K Ideal Gas Law b Find the volume of 85 g of O 2 at 25°C and kPa. = 2.66 mol WORK: 85 g 1 mol = 2.66 mol g PV = nRT (104.5)V=(2.66) (8.31) (298) kPa mol L kPa/mol K K V = L IDEAL GAS LAW
Gas Stoichiometry use at non-STP Conditions
Gas Stoichiometry b Moles Liters of a Gas STP use 22.4 L/mol (Avogadro’s Law) Non-STP use ideal gas law b Non- STP Problems Given liters of gas? start with ideal gas law Looking for liters of gas? start with stoichiometry conversion
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 stoichiometry and calculate moles of CO 2. Plug this into the Ideal Gas Law to find liters. x x
WORK: PV = nRT (103 kPa)V =(0.052mol)(8.31 L kPa/mol K )(298K) V = 1.25 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 = 8.31 L kPa/mol K
WORK: PV = nRT (97.3 kPa) (15.0 L) = n (8.31 L 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 = ?n = ? T = 21°C = 294 K R = 8.31 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 = 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. x x