PV = nRT PV = nRT
PV = nRTPV = nRT
Molar VolumeMolar VolumeAvogadro’s Principle - equal volumes of gases at same
T and P contain equal numbers of particles (equal number of moles)
one mole of any gas at STP has a volume of 22.4 L
1 mole H2 = 22.4 L at STP 1 mole CO2 = 22.4 L at STP 1 mole CH4 = 22.4 L at STP
H2CO2 CH4
Would the mass of this 22.4 L of gas be the same for all gases?
No!!!!!!!
Molar mass is equal to mass on periodic table.
22.4 L = 1 mole = mass (g) on periodic table
one mole of any gas at STP has a volume of 22.4 L
1 mole H2 = 22.4L at STP 1 mole CO2 = 22.4 L at STP 1 mole CH4 = 22.4 L at STP H2 CO2 CH4
2 g 44 g
16 g
Volume Ratios = Molar ratios Volume Ratios = Molar ratios in balanced equationin balanced equation
N 2 + 3H2 2NH3
1 mole nitrogen reacts with 3 moles hydrogen to produce 2 moles ammonia
Or 1 liter nitrogen reacts with 3 liters
hydrogen to produce 2 liters ammonia
Remember Combined Gas lawRemember Combined Gas law
P1V1 = P2V2
T1 T2Since number of molecules is directly proportional
to volume, it too goes on bottom of equation
P1V1 = P2V2
T1n1 T2n2
P1V1 = constantT1n1
Plug in standard temperature,pressure, volume, & # of moles to find constant
(1atm)(22.4L) = constant (273K)(1mol)
.0821 atm L = constant K . Mol
PV = nRTPV = nRTP = pressure (atm or kPa)V = volume (L or dm3)n = number of molesR = universal gas constantT = temperature (K)
Universal Gas ConstantUniversal Gas ConstantR = 0.0821 L-atm
mole-KR = 8.31 L-kPa
mole-K (1 dm3 = 1 L)
Units in equation must all match
Sample ProblemSample Problem
A rigid steel cylinder with a volume of 20.0 L is filled with nitrogen gas to a final pressure of 200.0 atm at 27oC. How many moles of gas does the cylinder hold?
PV = nRTPV = nRT
V = 20.0 L N2
P = 200.0 atmT = 27oC +273 = 300 K
R=
n = ?
0.0821 L-atm Or 8.315 L-kPa mole-K mole-K
PV= nRTPV= nRT (200 atm)(20 L N2) = n (.0821 atm-L)(300 K) K-mol
(200 atm)(20 L N2) = n
(.0821 atm-L)(300 K) K-mol
n = 162 mol N2
How many grams NHow many grams N2 2 is 162 mol?is 162 mol?
Periodic table mass of nitrogen = 14 g N2 = 28 g
162 mol ( 28 g ) 1 mol N2
= 4,536 g N2
Sample Problem 2Sample Problem 2
A deep underground cavern contains 2.24 x 106 L of methane gas (CH4) at a pressure of 15.0 atm and a temperature of 42oC. How many grams of methane does this natural gas deposit contain?
V = 2.24 x 106 L CH4
P = 15.0 atmT = 42oC +273 = 315 KR = .0821 atmxL/molxK? grams
PV = nRT or PV = nPV = nRT or PV = n RT RT
(15.0 atm)(2.24 x 106 L CH4) = n (315K)(.0821 atm-L/K-mol)
n = 1.30 x 106 mol CH4
CH4 = 16g
16g1 mol CH4
= 2.08 x 107 g
A really, really difficult one now!A really, really difficult one now!
How many liters of ammonia (NH3) gas would be produced at STP if 5.00 g of hydrogen reacts with excess nitrogen?
N 2 + 3H2 2NH3
PV = nRT PV = nRT
At STP volume of NH3 produced?
P = 1.00 atmV = ?R = .0821 atm-L/K-molT = 273 Kn = 5g H2 ___mol NH3
?
N N 2 2 + 3H+ 3H22 2NH 2NH33
5 g H2 (1 mol H2)(2 mol NH3) 2 g 3 mol H2
1.67 mol NH3
P = 1.00 atmP = 1.00 atm, , V = ?V = ? n = 1.67 mol NHn = 1.67 mol NH33
R = .0821 atm-L/K-mol R = .0821 atm-L/K-mol T = 273 KT = 273 K
V = nRT P(1.67 mol)(.0821 atm-L/K-mol )(273K) (1.00 atm)
V = 37.4 L